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"Sunlight—I've been dreaming of it for months, but it's hard to enjoy alone. The crash seems so long ago now. Father was right. We shouldn't have gone so deep. They do not want us down there. Despite my best eforts, ill health is taking hold of me. Margarite and father are already part of this incredible planet. It's reassuring to know that when I go, I'll join them. Until then... well, there's always the view.."
Bart Torgal

Subnautica is a survival game developed by Unknown Worlds Entertainment, creators of the well-received Half-Life mod Natural Selection and its sequel. Having spent almost four years in Early Access, and with its V1.0 deadline pushed back five times - from September 2016 to January 2017, then to February 2017, then to May 2017, once more to September 2017, and finally to 2018 - the game has fully launched on PC as of January 23, 2018. It receives one stable update per month and regular small updates for people who play in experimental mode. The game is available for the PC, Xbox One, and Mac, with a PS4 port planned for after V1.0 because the PS4 has no Early Access program.

The game is set on an alien ocean world, designated Planet 4546B. The player is the sole survivor of a crashed capital-class ship named the Aurora. The lifepod with which you escaped the Aurora's destruction is equipped with a fabricator, which you must use to cook fish, disinfect water, craft tools, and more. You must explore the underwater landscape of Planet 4546B to find resources and blueprints, build bases and vehicles, and discover just why the Aurora crashed in the first place, all the while trying to survive the dangers of the deep. All the same, Planet 4546B is filled with strange and beautiful biomes, inhabited by a rich collection of creatures that are no less fascinating than they are dangerous.

A currently unnamed Expansion Pack has been confirmed to be in development, set in the Grim Up North of 4546B.


Subnautica contains examples of the following tropes:

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    #-C 
  • 11th-Hour Superpower: The penultimate story objective contains blueprints for ion batteries and ion power cells, which provide five times as much juice as their basic counterparts. A Repulsion Cannon with such a battery installed doesn't deal more damage but can fire 100 shots before needing a reload, and the Cyclops' power reserves become so vast that activating the Deflector Shields or the Silent Running mode causes much less of a headache than it did before.
  • Abandoned Area: The various abandoned bases. The Sparse Reef also invokes this when the PDA questions why it barely features any life.
  • Ability Required to Proceed: Many areas are, if not impossible, at least extremely impractical to access without the right equipment. For example, the crash site of the Aurora is blanketed with radiation leaking from breaches in its reactor shielding and can only be approached safely if wearing a suit lining rated for radiation resistance. Certain depths are difficult to plumb without sufficient oxygen reserves and a rebreather or a vehicle rated to withstand the pressure at that depth. Some items and fragments are locked behind doors that need to be cut open with a laser cutter, etc.
  • Abnormal Ammo: Stock in trade of the Propulsion Cannon, which can lob anything you care to load into its energy field at considerable velocity. With nerves of steel (or an Alien Containment and some patience), it can harness the explosive power of the Crashfish into a formidable weapon.
  • Absurdly Sharp Blade: The survival knife, which can cut through solid pieces of coral like butter.
  • Acceptable Breaks from Reality: Several.
    • Decompression sickness is not an issue in this game. Given that the protagonist can only stay under water for 45 seconds (plus 30 seconds more for each air tank at the cost of speed and inventory space) it would be a little much to require you to wait an hour each time you needed to ascend 30 meters. You can also enter and leave vehicles/bases at will without worrying about pressure differences. Assume the suit compensates somehow and call it a day.
    • Hatches to get in and out of bases and tanks are a single porthole rather than an airlock. Moving around would be greatly hindered if you had to wait each time or, in the case of the tanks, be blocked off on one side of the room by the extra space needed for the airlock. Just assume that the porthole also generates a specialized force field to keep water out somehow and don't think of it any further.
    • Diving speed in real life is slowed down by arm movement, but the protagonist uses their arms constantly. This is done to give the player better visual feedback.
    • You can't improve a submarine's crush depth by hundreds of meters via what is essentially chip tuning. An upgrade like this would require extensive redesigning and strengthening of the hull at the very least. Same goes for installing torpedo tubes. Both options are lumped in with all the other performance upgrades for the sake of providing one streamlined game mechanic (although it would've been nice to have some visual change to the hull at least when crush depth and armor upgrades are installed).
    • Light, and with that color, doesn't travel very far through water. Long wavelengths such as red are the first to be cancelled out. For gameplay purposes and a pretty gameworld, this is ignored.
    • The two moons of the planet should make movement and navigation almost impossible due to their effects on the weather. Instead, the planet has a very calm ocean and the moons simply form a very pretty sky and major light source at night.
    • Although it can come across as seriously immersion-breaking for some, the Player Character's invulnerability to water pressure is mostly a welcome featurenote . The game is unforgiving enough as it is without you being unable to repair or, if need be, Abandon Ship if push comes to shove.
  • Action Bomb: The Crashfish, as the PDA puts it, takes a "Mutually Assured Destruction" approach to defending its nest. It'll chase after any player that approaches its cave and literally blow up in their face.
  • Action Prologue: The game opens with the Player Character strapping into a lifepod to a cacophony of alarms, with no knowledge of what's going on except that it's time to Abandon Ship. Once you've made planetfall and put out the fires in the pod, you can finally take a breather and start planning your objectives.
  • Adaptive Ability: The lifeforms of 4546B are implied to evolve at a much faster rate than earth lifeforms as according to the PDA many of the current organisms developed in just the last thousand years, something that would take millions for earth creatures.
  • Adventure-Friendly World: A couple of common survival blueprints are not available to the protagonist because their PDA files have become corrupted. Fragments or examples of the items need to be found and scanned before they become available for construction.
  • Alien Blood: Originally averted, but now played straight, with the planet's creatures having yellow blood.
  • Alien Sky: There are two moons in the sky, one of which is extremely large, resembles Mars, and often causes solar eclipses.
  • All Flyers Are Birds: Zig-zagged; the only flying creature you see looks for all the world like a flying manta ray, but the scanner says that its "fins" are actually composed of oddly-shaped feathers.
  • All Planets Are Earthlike: Although this one has water covering nearly its entire surface, as opposed to a measly 70% of it.
  • The Alliance: PDA entries mention the Trans-System Federation, which exists as an authority above the Trans-Govs, of which Alterra is one. According to the Charter, the TSF exists as a military police force dedicated to preventing conflict among its members and guaranteeing relative freedom of movement within its borders. Said Charter is why the Sunbeam is obligated to respond to the distress call from the Aurora, and thus what gets them killed.
    • The TSF is also why the Aurora just so happened to be carrying a dedicated contingent of underwater gear: their secondary mission was to investigate 4546B in search of the Degasi as a favor to the Mongolian Empire.
  • All There in the Manual:
    • Thanks to your tight-lipped protagonist and a fairly limited number of radio messages received from other survivors and the occasional Warper squad, piecing together the game's plot from audio and events alone is next to impossible. If you want to learn the whole story, you'll have to spend some time digging through the exhaustive in-game database, with particular emphasis on anything concerning the precursors (or "aliens", as the PDA designates them) and the Kharaa bacterium.
    • The game actually invokes this right at the beginning when your PDA reboots in emergency mode. Instead of giving you the run-down on what to do after your life pod just crash-landed on an uncharted planet, it simply advises you to read the relevant database entries. Most of what it tells you as the story progresses is similarly useless from a utility perspective, and nearly everything important to your survival must be gleaned from text messages.
  • Almost Out of Oxygen: There is a high possibility of this occurring while harvesting resources or trying to escape danger.
  • Amazing Technicolor Wildlife: The fish in the game are really colorful. Most of the game's flora and all but three species of fauna are bioluminescent.
  • An Interior Designer Is You: You can construct your own bases, decorating the interiors with everything from the crucial (fabricators, lockers) to the frivolous (vending machines, benches). Overlaps with And Your Reward Is Interior Decorating because you need to scan most pieces of furniture before you can build them.
  • Anti-Frustration Features:
    • Alien Tablets, unlike practically every other item in the game, give a blueprint to fabricate more of them as soon as you pick their specific color up. In other words, these "keys" to unlock more Precursor areas and advance the story are infinitely manufacturable (with relatively uncommon materials) and don't even need to be scanned, so even the most scatter-brained player can avoid being locked out. Convenient if you lose them. Note that eventually players are required to build further tablets, rather than being optional.
    • The blueprint for the rad suit is made available "for your convenience" immediately after the Aurora's remains go nuclear.
    • Unlike his vehicles, the Player Character doesn't have a crush depth. He can dive as long and deep as his oxygen lasts, and he can exit damaged vehicles for repairs at any time regardless of the depth.
  • Apocalypse How: The Sea Dragon Leviathan's attack on the Secondary Bio-Research Facility in the Lost River released the Kharaa bacterium onto the planet. The gigantic crater in which Subnautica takes places is the only location on the entire planet where any life remains, thanks to the Sea Emperor Leviathan distributing small doses of the enzyme that gives it its immunity through Peepers and the Alien vents. Kharaa most likely culminated in a Class 1 or 4 for the local fauna. And this is a mere drop in the bucket, given Kharaa wiped out about 143 billion individuals on Precursor worlds.
  • Apocalyptic Log: Abandoned PDAs from the other Aurora survivors, as well as those of the Degasi crew, can be found in the various ruined lifepods and bases, detailing their owners' respective plights.
  • Arm Cannon: The P.R.A.W.N. suit features mounting points for subsystems on both of its arms, which can be fitted with a Propulsion/Repulsion Cannon or Torpedo Launcher.
  • Artistic License – Astronomy: The two moons of the planet are in an extremely low orbit judging by their size and the speed that they cross the sky. The gravity from Earth's moon causes a daily high and low tide at a much further distance out. Two moons of that size and proximity would cause titanic and unpredictable waves, with fluid forces that would make movement and navigation almost impossible. Instead, the planet has a very calm ocean and the moons simply form a very pretty sky and major light source at night.
  • Artistic License – Chemistry: The brine streams in the Lost River are as caustic as acid; merely skirting them while swimming around the area deals considerable damage. Brine in Real Life has no detrimental effects on the human skin no matter the concentrationnote , much less so if the swimmer is clad in full-body diving gear. Brine baths have actually been used for medicinal purposes since time immemorial, mostly to treat various skin diseases.
  • Artistic License – Engineering: Seabases make some concessions to the needs of an underwater habitat, requiring structural reinforcement to not fall over or apart, and the lower a seabase is built the higher the water pressure on it and greater the reinforcement required. However, for simplicity of gameplay, the reinforcements and weaknesses have nothing to do with one another. The game simply totals up the "strength" value of certain parts and subtracts the "weakness" value of other parts, and so long as they balance out the base is stable. An observation dome might be a major weak point, but slapping some lithium-reinforced panels on a moonpool on the other side of the base will more than compensate for it.
  • Attack Its Weak Point: Not a gameplay trait but a programming trait. Very large creatures do not have a full-body hitbox and something like the Stasis Rifle won't affect them if they're hit where they don't tangibly exist. This is especially true for the Reaper Leviathan, which despite its size only counts for its head. You can swipe ineffectually at its tail, but you'll only get hit noises and blood fx spawning near its head.
  • Attack of the 50-Foot Whatever: Hostile Leviathans in a nutshell. There are six Leviathan-class lifeforms in the game, three of which are aggressive, and the smallest of these - the Reaper - measures 55 meters in length (your largest vehicle sits at 54m/177ft). It's dwarved by the adult Ghost Leviathan's 107m (even the juveniles are bigger than Reapers at 67m) and the Sea Dragon with its 112m. The game's largest creature, the Sea Emperor, is estimated to measure 160-200m in length, although thankfully it doesn't attack.
  • Audible Gleam: When you pick up gold or diamond.
  • Awesome, but Impractical:
    • There's no doubt that the Cyclops is awesome, but it's also large and unwieldy, which can make it difficult to navigate many of the tight deep sea cave systems it's meant to explore. This isn't helped at all by the multiple Leviathans down there that it can't outrun like it could in open waters, meaning you'll have to be ready to make repairs on the fly while surrounded by scorching temperatures and hostile fauna. Veteran players with intimate knowledge of the cave layouts and entry/exit points may have an easier time, but an upgraded Prawn suit is much more versatile when it comes to exploring the game world's deepest reaches. Unfortunately, you must build a Cyclops at some point to gain access to the Cyclops Shield Generator tech, which you need to complete the Neptune Rocket and finish the game.
    • Tank-grown crashfish, used as explosive ammo for the propulsion cannon, constitute the most powerful actual weapon in the game. Unfortunately, each crashfish takes up four tiles (2x2) in your Grid Inventory, so you won't be able to carry more than one or two with you at any given time if you plan on lugging some salvage back home as well. They also need to be manually loaded into the cannon like any other item, which can cost you the second that makes the difference between blowing some predator to smithereens, blowing yourself up as well, or simply being Eaten Alive.
  • Bioluminescence Is Cool: During the night and the underwater cave sections, certain fish and plants will have a luminescent glow. This will help you see where you're going. This is especially prominent in the Jelly Shroom Caves, Bulb Zone, and Grand Reef, thanks to their massive glowing flora.
  • Bizarre Alien Biology: Everything! Special consideration goes to the Ampeel for its electro-spikes all over its body, the Gasopod for both its gasmask face and tail-sack, the Reaper for its face clamps, the Sea Treader which uses its snout as its third leg, and the Crabsquid for its everything.
  • Bizarre Alien Sexes: Everything on the planet is of a single egg-laying sex that can either self-impregnate or mate with any other instance of its species.
  • Black Humor: The game has a rather grim sense of humor. Special note goes to the PDA descriptions, which range from poking fun at your current situation to relaying horrific information in a matter-of-fact way. Which ultimately culminates in the Brick Joke cum Yank the Dog's Chain that is The Stinger, as detailed under those entries below.
  • Blown Across the Room: The repulsion cannon packs an impressive wallop for something so small. It doesn't deal much damage, but the force it applies is sufficient to push even the largest non-Leviathan beasts back several dozen meters. Smaller creatures like Stalkers turn into a Twinkle In The Sky when shot from below in shallow waters, and it can take quite some time before they fall back into the sea.
  • Border Patrol: Adult Ghost Leviathans spawn in the Void/Crater's Edge, with even the PDA saying exploring said biome is "not recommended." At sufficient distance if you somehow survive, you'll allegedly be teleported to Lifepod 5.
  • Boring, but Practical:
    • The Seamoth mini-sub is the first true vehicle you'll probably unlock. While it lacks the Prawn's utility and sturdiness, it's quite fast, reasonably cheap to build and extremely manoeuvrable even in tight spaces. It boasts decent storage capacity for something so small and can even be equipped with up to four torpedo launchers. Its utility upgrades are also quite helpful against anything including Leviathans. Until the story absolutely forces you to descend to depths below the Seamoth's maximum crush depth of 900m, the little fellow is generally a much more convenient exploration tool than the huge, supremely unwieldy and very expensive Cyclops, or the Prawn with its serious trouble in getting out of deep sea trenches without some expensive upgrades.
    • Beacons are little gizmos you can drop in the water to mark points of interest - an invaluable asset in a game that lacks a map or any other waypoint system. They're cheap to build, their blueprint is easy to find, they only take up a single inventory slot, and they can even be given individual names to help you keep track of what's what. New players should never leave base without one or two beacons in their pack, especially in the early game stages when you're still discovering new stuff around every corner, but they remain very useful throughout the whole game. That they look suspiciously like Aperture turrets is just icing on the cake.
  • Bothering by the Book: Alterra is apparently quite guilty of this In-Universe, given Captain Avery Quinn's complaints about them. Under the terms of the Trans-Gov charter, ships are obligated to investigate and respond to any distress beacon they come across, with harsh penalties for failing to render aid. Alterra ships have developed a reputation of abusing this to get other people to give them utterly non-essential supplies if they run out.
  • Brick Joke: Early in the game, the PDA explains that everything on the planet is property of Alterra and that you will be billed for everything you used, with the bill running at three million credits. Come the Stinger after the credits roll, You have made it back safely, but Alterra refuses to allow you to land your rocket until the debt you owe for the resources used on 4546B is paid, which is now at a grand total of a trillion credits.
    • On said escape rocket, upon exiting atmo you enter a debris field from the Aurora. A panel breaks off and the protagonist raises their hand defensively, having learned about getting smacked in the face by loose panels from the prologue.
  • Charged Attack: The Seamoth perimeter defense system unleashes a powerful electric pulse that stuns and damages nearby creatures, up to and including Leviathans. Holding down the fire button continually increases the pulse's range but consumes ludicrous amounts of energy (up to 15% of the sub's power cell at full power; a standard shot consumes 1% to fry everything in a ten meter radius).
  • Checkpoint Starvation: There are no checkpoints. Each game only has a single manual save slot and nothing else. Dying warps you back to the last habitat you visited, but that's about it. Be very careful about when, where and under which circumstances you save your game, or you might realize too late that you trapped yourself in a dead end with no way out, not even by reloading.
  • Chekhov's Gunman: The Peepers. Being such a common prey animal makes them perfect for transporting Enzyme 42 out of the Sea Emperor's containment facility and into the local ecosystems, thereby saving most of the local fauna from dying of Kharaa.
  • *Click* Hello: The Crashfish make a sound that sounds a lot like this when popping out of their nests. The chase noise they have can be best described as a gurgling rising in pitch until it goes boom.
  • Cloning Body Parts: New organs and the like are a regularity for people who have the money for it in the future world of Subnautica. A guaranteed supply is one of the perks of Alterra higher-ups and as Paul Torgal says: "I turned 80 years old last week. I thought I had another 80 in me yet. Stuck here, there's no swapping out my liver when the old one fails. Down here, I'm mortal."
  • Colony Drop: A meteor fell on Planet 4546B in the Dunes 1,000 years ago, which is implied to have had long-lasting effects. The PDA implies that the meteor is what started the extinction event on the planet. The Kharaa only made it worse.
  • Company Town: Downplayed. Some of the info you can download from PDAs highlights the Mega Corp. nature of Alterra, who are so big that they practically constitute a form of government. At some point in the game, your AI assistant can remind you that everything you collect while stranded planetside belongs to the company by default, with a reminder that you will owe compensation for everything you use to survive. The message then provides an estimate of your running total which is at 3 million credits, and by the end of the game your total will have gone up to a trillion. Maybe surviving the crash wasn't such a stroke of luck after all....
  • Continuing Is Painful: When you die (on anything but the hardest difficulty, which features Perma Death), you're teleported back to your last habitat and any items you picked up since then are lost. If you died a death moments after stepping outside your pod, not such a big deal, but if you've spent several minutes swimming to and fro and gathering resources, it can be quite exasperating. In the worst scenario, you've lost your vehicle during your trip and are warped back to a base too deep to reach the surface without aid.
  • Convection Schmonvection: Downplayed. There are volcanic vents which have frequent outbursts of hot water and rock fragments. These can't hurt you, but getting too close (as in right next to the glowing crater) will cause you to take heat damage. It should also be noted that according to in-game temperature readings, it isn't even that hot — harmless Thermal Vents tend to be hotter even in the Lava Zone than the bright red, damaging craters (vents spiking to 80 C or higher, while some harmful and seemingly hot spots may be as low as 50 C).
    • Whenever you open a damaged bulkhead with the laser cutter, you're cutting through ten inches of reinforced metal (most likely titanium). The hole's edges glow brightly orange to red for quite some time, but you'll never take any damage from touching them.
  • Cool Boat: All of the craftable ships, but the crown of this trope goes to the Cyclops submarine, which is also a mobile base for the player.
  • Cool Starship: The Aurora, which ends up exploding, giving you entry, and placing a burden on you to repair the reactor containment field, or else you'll be overrun by deadly radiation.
  • Crapsaccharine World: Humanity is far advanced, has explored and controls most of the galaxy and can make nearly anything with their extensive replicator-like technology. Yet all of it is controlled and maintained by Mega Corps and humanity basically lives in a strict capitalist/contractual mindset where even something as simple as a boyfriend/girlfriend relationship requires an extensive contract agreement!
  • Crate Expectations: Mostly stuff from the Aurora. You need a Propulsion Cannon or Repulsion Cannon to move them out of the way. Storage crates can be manually opened for goodies.
  • Creature-Breeding Mechanic: You can breed fish as long as you have two to start with and an alien containment unit to place them in. This is useful to create a steady food supply or a steady bioreactor fuel supply.
  • Crew of One: In-Universe, a selling point for the Cyclops is that, despite being designed for a crew of three, it can be operated by a single person if the need arises. This has made it very popular among deep sea exploration teams, and is a tremendous boon for the player.
  • Critical Research Failure: In-Universe. The Precursors have been trying to hatch the Sea Emperor's eggs for centuries (especially since they need them to peacefully cure the Kharaa and stop having to resort to, you know, genocide). It turns out that the eggs aren't being raised in an environment meant for babies, and that the incubators they were placed in had their environment configured for what adults would inhabit. As such, it takes the player (again) to fix this. Truth in Television as in Real Life most giant sea creatures do, in fact, have different ideal living conditions as larva or juveniles before moving to the ones they prefer as an adult. Even worse, the Sea Emperor was trying to explain this to them, but they were deaf to her telepathic communications. Thankfully, Ryley is not, and can be instructed on how to get them to hatch. note 
  • Curb-Stomp Battle: Unless you have a P.R.A.W.N. suit with the drill upgrade, a confrontation with any hostile creature larger than yourself will almost inevitably be this. Your only real option is to flee.
  • Cute Machines:
    • The Seamoth is what you'd probably get if Apple were to branch out into submarine construction. It's small, it's almost completely spherical and just all-around adorable to behold.
    • The head-sized construction drones that come with the Mobile Vehicle Bay and the Neptune rocket launch platform are another excellent example.

    D-L 
  • Damage Is Fire: Your vehicles start sparking and smoking when they're heavily damaged, and the Cyclops actually starts burning from the inside, forcing you to drop everything and put the fires out lest you suffocate. There's even a dedicated fire suppression system you can build and install to making this easier.
  • Deadly Gas: Gasopods can produce gas pods that explode after a short while to create a deadly, yellow-green butt. If the player is quick, they can grab one or two pods before explosion and use them in torpedoes.
  • Death World:
    • The Dunes biome is home to eight Reaper Leviathans, and entering it will prompt the PDA to skeptically ask you if what you're doing there is worth the risk.
    • The Inactive Lava Zone and Lava Lakes are scorching hot, home to Lava Lizards and Sea Dragon Leviathans, and infested with Lava Larvae that drain electricity from your vehicles, potentially leaving you stranded a kilometer underwater. Visibility is also low, making it difficult to find your way out even if you do still have power.
    • The Crater Edge surrounding the map is an ecological dead zone that contains only two forms of life: microscopic, and leviathan-class. If you enter it, up to three Ghost Leviathans will appear and chase you relentlessly until you're dead or out of their territory. The PDA implies that this biome spans much of the planet.
    • The Crash Zone will kill you in under a minute if you enter without a radiation suit following the drive core of the Aurora exploding and is also stalked by eight Reaper Leviathans. Unlike most of the other deadly biomes, players can enter the Crash Zone very early in the game, forcing them to face Reaper Leviathans without the Seamoth's perimeter defenses or PRAWN suit. Prepare to be Eaten Alive...
  • Deflector Shields: An upgrade for the Cyclops gives you one. The bubble effect only covers the forward canopy, but the effect is around the entire sub. It zaps Lava Larvae, renders the sub invulnerable to damage from even a persistent Sea Dragon, and also seems to prevent pressure crushing the hull. Too bad it drains power like nobody's business. It's required to build the Neptune Escape Rocket, as it allows you to survive the orbital debris field.
  • Derelict Graveyard: The volcanic crater/plateau that the Aurora crashed on is one, albeit it only consists of a single ship. Most of the Aurora landed in a large wreck that looms partially above the water, but large sections of the ship detached either during its fall or on it's impact, sending entire deck assemblies scattered about the ocean floor. Many of these still have their interior compartments relatively intact, and salvaging them is useful for basic supplies and essential for unlocking additional blueprints.
  • Developers' Foresight:
    • If, by some absolute miracle (or use of console commands or simply not repairing the radio until the end), you manage to shut down the Quarantine Enforcement Platform before the Sunbeam arrives, not only will the ship not be shot down, but Captain Quinn will send you a unique message about being unable to penetrate the immense orbital debris field left behind by the attack on the Aurora.
    • If, by some other absolute miracle, you manage to fully scan a Reaper Leviathan without getting Eaten Alive, the data bank entry will contain a motivational note from your PDA to congratulate you on your unlikely success.
  • Difficult, but Awesome: The Cyclops and PRAWN. They are essential for the depths of late game where the Seamoth can't go, pack a punch, and have high customization options. They are, however, also slow and bulky and energy-draining, lacking the scouting qualities of the Seamoth. Specifically, compared to the 360 degree mobility, the Cyclops handles like a supermarket trolley, and the PRAWN suit - whilst boasting impressive armor - has little to no vertical maneuverability, making it easy to jump off an edge and spend a lot of time crawling back up.
  • Dishing Out Dirt: More or less the purpose of the Terraformer before it was removed for technical and gameplay purposes.
  • Doomsday Device: While exploring the Quarantine Enforcement Platform, you can scan a malfunctioning one. Despite being small enough to hold in your hands, the data readout indicates it packs enough oomph to destroy the entire solar system.
  • Dummied Out: Occasionally you can see ideas from earlier Early Access builds floating around in the 1.0 release.
    • One of the first major things to be removed, mourned by players and developers alike, was the Terraformer, which could move terrain from one part of the planet to the other. It was removed for both technical and story reasons, as the plot changed from "make the planet inhabitable" to "escape the planet". Players with old Early Access saves will still retain the chunks of land removed or added to their game, although the updated map can make bases inaccessible.
    • As of the 1.0 update, the Thermometer is still in the Blueprints, but can't be built.
  • Dying Alone: The protagonist is at risk of this. From data downloads, it is known or implied that this has happened to almost everyone who didn't die in the crash.
  • Earn Your Happy Ending: For both the player and the mysterious race known as the Precursors. In the player's case, after fighting through a world full of dangerous creatures and leviathans, being infected to an advanced stage of The Plague, and losing a trade vessel in their sake, they construct a rocket and escape. For the Precursors, although they lost the one thing that they really wanted to protect, it brought forth a new generation of Emperors that will produce the enzymes necessary to finally cleanse the planet of the bacteria, and will soon no longer have the need to shoot down any more ships.
  • Easter Egg: A Natural Selection 2 poster can be found inside an explorable Aurora compartment in the Grassy Plateaus. You can even pick it up and hang it in your base.
  • Easy Logistics: Subnautica being a survival game, it heavily averts this. Keeping yourself alive and your base running requires careful planning and consideration not only about how, when and where to invest your scarce resources, but also about figuring out where to find them first.
    • The two most powerful and reliable reactor models in the game must be provided with a constant fuel supply. If they run out, your base including its oxygen production simply stops working.
    • Mounting longer expeditions necessitates sacrificing generous parts of your limited storage capacity for vital supplies like food, water, batteries, medkits and tools, all of which need to be crafted from varying amounts of resources. This naturally limits the amount of salvage you can carry home from your trips, making storage capacity upgrades in your vehicles quite helpful during mining forays.
    • A major part of the benefits of advanced technology is that they reduce the strain on your supply lines. Alien containment tanks allow for the breeding of fish that can be eaten or used as bioreactor fuel. Planters are invaluable for growing even more food and biofuel, as well as crucial crafting resources that otherwise require venturing deep into the game's most dangerous areas. Water purificators provide you with a limitless supply of high-quality water, plus salt for crafting food rations without an expiration date.
    • One of the few aversions is the repair tool. You don't need actual resources to repair stuff, only a charged battery in the tool.
  • Effortless Achievement: The full release still has a few of these. Getting your feet wet and consequently building your first base piece, which takes a little effort. You'll unlock achievements for building the three currently implemented vehicles and exploring story required locales. though they seem to be bugged, building the escape rocket and launching the time capsule also are achievements. The Neptune is pretty resource heavy but the time capsule is literally a button press to launch, and usually launches automatically with the rocket's ignition.
  • EMP: The crabsquid's signature attack, capable of temporarily disabling anything electric in a considerable radius. Trying to get away from two or more crabsquids in any vehicle will make you feel like you're stuck in a stop-motion movie shooting.
  • Empty Room Psych: Downplayed but present in the Void, the bottomless abyss around the crater that constitutes the game world. There's absolutely nothing there except water, darkness, and silence... and an army of Ghost Leviathans just waiting to tear you to pieces if you dawdle in their territory for too long.
  • Enemy Scan: One of the core tools is a scanner to scan just about everything, hostile fauna and flora included. The results of each completed scan are stored in the PDA, which therefore in part serves as a Monster Compendium.
  • Enemy Mine:
    • Different species of predators are just as likely to territorially attack each other as they are to attack you. This is especially visible in the second Degassi seabase, where Warpers and Crabsquids will fight over the exclusive right to harass you while you're exploring it.
    • There is a taming mechanic. Holding Peepers or other small prey fish in your quick-slots will let Stalkers eat them, and they won't attack you. For a while. They even occasionally bring piles of scrap.
    • It seems to work for Reaper Leviathans as well, as people have tried so and uploaded the results to youtube, but don't count on it saving your ass. Said videos feature an animation where the player raises their arms, the screen goes black, but there's no You Died message. The Reaper removed all prey fish from your inventory and spat you out.
  • Equipment Upgrade: There's a modification station, a vehicle modification station, and two specialized fabricators to improve your stuff.
  • Everybody's Dead, Dave: By the time the main game's events begin, every mentioned character except the player and the Sea Emperor, who is the Last of Their Kind after an incident which left 314 specimens of her species dead are dead or missing.
  • Everything Is An I Pod In The Future: All Alterra equipment is shiny white, with smooth surfaces and rounded edges and corners. Any larger sea base you build will inevitably look like an Apple designer's wet dream.
  • Everything Trying to Kill You: Averted, particularly in the Safe Shallows: there are lots of Passive fish which will never harm you at all, and also plenty of Defensive fish who will only attack if you get too close or bother them. The truly Aggressive species are actually a minority, but they're still almost omnipresent and extremely dangerous even so, seeing how even a single one can often kill you in a flash.
  • Exactly What It Says on the Tin:
    • The scanner data for the pink mushroom describes it as "definitely a mushroom". Most of the names of the fish are pretty descriptive as well; the Boomerang indeed just looks like a boomerang.
    • This gloriously helpful item description: "Fire extinguisher: extinguishes fire." Who'd have thought.
  • Family-Friendly Firearms: Lethal firearms are forbidden from being created by the fabricator (something about a massacre on Obraxis Prime). You can arm some of your submersibles with torpedoes, but the only true handheld weapon is the non-lethal stasis rifle.note 
    • The only true firearm is an alien rifle suspended in an impenetrable display case within the Quarantine Enforcement Platform.
  • Fastball Special: Any creature caught and flung by the Propulsion cannon, pair it with tank-grown Crashfish for explosive results.
  • Final Death Mode: Hardcore mode. Exactly like Survival mode, except you only have one life and have no oxygen warnings. Forget to check your meters at your own peril.
  • First Person Snapshooter: Optional. Pictures taken can be used as decoration in one's base by means of the Picture Frame.
  • Flower Mouth: The Mesmer has a mouth that splits open four ways to reveal four tentacle-like appendages lined with teeth that lead to its actual throat.
  • Fluffy Tamer: The secondary function of the Alien Containment module, as any predator you hatch inside it will be docile towards you. This continues to apply if you release them from the tank and they become full grown. Ever wanted a pet Ampeel, Crabsquid or Boneshark? Now's your chance.
  • Fragile Speedster: The Seamoth is the fastest mode of transportation in the game, but a few collisions with the environment or attacks from aggressive fauna is enough to turn it into a pile of scrap metal.
  • Friend to All Living Things: The Sea Emperor. She's entirely harmless, the normally predatory species living in her enclosure are peaceful, and she's actively trying to fight the infection of the planet.
  • Forbidden Zone: A few would qualify, but the Crash Zone is a prime candidate. Reaper Leviathans hunt in the surrounding seafloor, and after the Aurora's reactor containment field explodes, the area fills with radiation and cannot be explored without a radiation suit.
    • Then there's the Crater's Edge, AKA the Void, aptly named because the seabed steeply dives into an inky abyss and it's populated by multiple Ghost Leviathans who want nothing more than to eat you and your Cyclops.
  • Foreshadowing: You'll encounter small pink creatures called Floaters who have attached themselves to small rocks. You can eventually find a huge island, as well as smaller underwater islands, being held afloat by huge versions of the same creature.
    • The wall of the escape pod says that the bacteria count in the water is high. One of the first items the player can craft is short-range scanner. After a while, upon scanning oneself, the display on the scanner reads "INFECTED".
    • The first data file on Peepers mentions they have a pointlessly enlarged nasal cavity designed to detect a single, very specific odor which absolutely nothing yet encountered produces. You can also spot Peepers emitting a strange glowing trail, which, if scanned, are coated in some strange substance which inhibits bacterial growth. It's designed to detect Enzyme 42, and is the first hint of the Emperor Leviathan's deliberate alterations to the Peepers to help it save the ecosystem from the Kharaa Bacterium. Those glowing trails are also streams of unstable Enzyme 42, bestowed upon them by the Leviathan and released via the Alien Vents.
  • Fungus Humongous: The Mushroom Forest and Jelly Shroom Caves.
  • Game-Breaking Bug:
    • A particularly nasty persistent bug occurs when you save your game, which causes any partially researched blueprint to lose all progress and force you to start over. It seems to have been fixed with the full release though.
    • There's still a lot of clipping issues even after the game went gold. The player can often fall through the seabed, even in a vehicle, requiring console commands to warp you away, often at the cost of your vehicle.
    • The P.R.A.W.N. Suit loses almost all of it's jet mobility and grappling-arm winch strength while outside of the water. If the player takes the P.R.A.W.N. onto dry land, exits the suit, saves the game, then re-enters the suit, it can lock the P.R.A.W.N. in the "out of water" state permanently, crippling its limited mobility even when back in the water. The only solution is to build a completely new P.R.A.W.N. Suit. Especially breaking as the P.R.A.W.N.'s jets and/or grappling-arm are almost required to get into the Lava Castle near the end of the game.
    • For anyone hoping to use your exosuit and incredible skills to kill a Reaper leviathan, you should probably give up hope. With the hull reinforcement upgrade a PRAWN might be able to take on a Reaper... except that almost every such battle ends with the Reaper clipping through the terrain and glitching your PRAWN into uselessness, whether trapped in the terrain or dropped thousands of kilometers below the world.
  • Gentle Giant: Some of the creatures you encounter will be this, such as the monstrous, loud, but harmless Reefback. You won't know unless you get spotted by them or go up to them, though.
  • Giant Enemy Crab: The ambiguously-scrapped Rock Puncher and the definitely-scrapped Grabcrab.
  • Giant Squid: The Crabsquid, which was implemented in the Machinery Update. Oh, and it can walk on the seafloor and produce EMP blasts.
  • Glowing Flora: Many deep-sea plants (this includes a tree) are just as bioluminescent as the rest of the living things living there. This was probably to exaggerate the stereotypical abyssal theme, since many bioluminescent creatures live in this biome in Real Life.
  • Going Critical:
    • The Aurora's reactor explodes, releasing lethal radiation in the surrounding area which will kill you without a Radiation Suit.
    • If your Cyclops suffers a Critical Existence Failure, you will have about ten seconds to abandon ship before it explodes.
  • Going Down with the Ship: An abandoned PDA reveals that Captain Hollister stayed onboard the Aurora until the very end, knowing that the survivors would need the ship in one piece in order to contact Alterra HQ.
  • Grappling-Hook Pistol: One of the PRAWN upgrades. Essential if you're taking it anywhere deep.
    • Fun for latching onto a Leviathan and going for a rodeo ride.
  • Gravity Screw:
    • The whole point of the Propulsion Cannon, a tool meant for picking up and moving/throwing small to medium-sized objects. Seeing how the thing is a barely disguised Expy of Half-Life 2's Gravity Gun down to a very similar look, this shouldn't come as a surprise.
    • The Quarantine Enforcement Platform has a vertical antigrav lift to facilitate movement between the ground floor and the sublevel a hundred meters below.
  • Greed: Paul Torgal's search for a resource-rich celestial body is what doomed the Degasi and as a consequence the Aurora and the Sunbeam. Justified as mining was his job, and no one could have expected to be shot down by an automated Orbital Defense Platform. His decision to go live underwater near richer mineral deposits (and sea monsters) is more clearly a bad choice instead of just an unlucky one.
  • Green Hill Zone: The Safe Shallows.
  • Guide Dang It!: Part of what makes Subnautica's survival atmosphere so intense is that you're told next to nothing upon starting a new game, and things barely improve from there on. There's no instructions, no tutorial, not even a friggin' map, least of all something like a questlog (or even quests to begin with). The only real HUD markers you get are from the few Aurora survivors, and that ends fairly quickly. Afterwards you're completely on your own, and unless you consult a guide, you can spend hours upon hours getting lost in subterranean tunnel systems, wondering if there's even a point in risking your life down there, and if there is, what you're supposed to accomplish in this place. May sound bad, but it makes for an epic adventure full of astounding discoveries.
  • Hazmat Suit: The whole of the Radiation Suit, the Radiation Gloves, and the Radiation Helmet. Lack one, and the radiation will harm you.
  • Heal Thyself: Medical packs will heal you completely and instantly. It's unknown if future updates will add tiers to your supplies, so you'll have to be more careful in the beginning when you can't make the strongest ones.
    • In the final release, Medical Packs only heal 50 points, but still do so instantly.
  • Hearing Voices:
    • The Mesmer will do this to you if you get too close.
    PDA: It is your primary directive to swim closer to that beautiful creature... Do not resist... Don't struggle...
    • The PDA entry says the pattern on its fins basically makes you perceive the most trustworthy source to tell you the above message. In the protagonist, that's obviously the PDA. Wonder what the other fish hear/perceive.
    • Your first encounter with the Sea Emperor is hearing its voice from nowhere. It's later shown that it speaks to you through telepathy.
    What... are... you?
  • Heel–Face Turn: In a meta example, the Cute Fish was the original Crashfish, a fish which hides inside a plant and pops out to charge at you and explode if you get too close. However, everyone agreed it was too cute, and rewrote the Cute Fish's AI as a pet which follows you around and chirps delightedly.
  • Hell Is That Noise:
    • The radio's beeping whenever it picks up a new message. The first few messages you get are distress signals from fellow survivors. As you go to explore, which is needed to continue the story and get more messages, you'll find out they all already have died. From that point on, the beeping becomes a grim reminder because you know it won't lead you to survivors but to their final PDA files often giving a good idea of how their final moments were. Then after a while, the radio starts picking up on messages that aren't from fellow survivors but from Warpers hunting for them. And for you.
    • It's not unusual to hear creatures before seeing them. The Reaper Leviathan's PDA entry ups the discomfort of its roar with the following line: "The deep roar emitted by the reaper at regular intervals is effectively sonar - if you hear it, the reaper can see you."
  • Hoist by His Own Petard:
    • The player can do this to themselves if they breed Crashfish and then set them loose outside their base. Sure, the fish won't attack you because it grew up docile, but it will attack other fish by suicide bombing them right next to the hull of your base, causing a breach, a flood, and a panicked flail as the player runs all over trying to find the hole. Why, no, this isn't inspired by a true story at all...
    • The Prawn Suit's grappling hook can be used to hitch a ride on Leviathans. While this can be quite entertaining, doing it to a Reaper will radically and permanently alter its patrolled area as it tries to shake you off. It's not uncommon for the beast to end up in a completely different biome including the Safe Shallows this way, and possibly way too close to your base for comfort. Players have reported up to three Reapers taking up residency barely 100 meters from their base because of this.
  • Homing Projectile:
    • Torpedoes will, if a Leviathan is present, immediately home in on them to the exclusion of anything else. Given how immensely dangerous Leviathans are, this is an extremely welcome quirk.
    • The spikes shot by Tiger Plants are semi-homing as well, capable of adjusting their flight path to a moderate degree.
  • Hope Bringer: The protagonist. Almost by accident, they complete the Precursor's work of saving the Sea Emperor population and stopping the Kharaa epidemic.
  • Hope Spot: Another ship, the Sunbeam, picks up the emergency distress signal from the Aurora and comes to help... only to share the Aurora's fate, being blasted out of the sky by the precursor gun. There are no survivors this time.
  • Hot Blade: One of the upgrades for the Survival Knife equips it with a heating element, causing the edges of the blade to glow red. Mostly this is used to kill and cook edible wildlife in one action, the upgrade actually reduces the damage dealt with the blade in exchange for its new ability.
  • Improvised Weapon: The developers (and, In-Universe, the Alterra company) intentionally made the game lack true weaponry besides Torpedos, but that doesn't stop particularly paranoid or violent players from taking revenge against the sea life.
    • The Propulsion Cannon, originally designed as a short range logistical tool, can be used to grab and toss crates at sea life, or to pick up smaller creatures and slam them against walls for lethal damage. There's also a variation on a PRAWN Suit's onboard storage to give it a sort of ammo magazine.
    • The Repulsion Cannon upgrade for the Propulsion Cannon completely removes the ability to pick things up, going directly to blasts of force. Of course this is intended as a self-defense tool to get away from animals, but it's still quite easy to smash a shark against the sea bed multiple times until it dies.
    • In the same vein, the Drill Arm is primarily an industrial harvesting tool, but three shrieking, grinding blades are remarkably handy for convincing a hungry Reaper Leviathan to seek out easier prey when applied vigorously and mercilessly.
    • Even the default Prawn Suit arms are quite powerful. A few punches to a Stalker will very easily kill it, even when the arms' primary use is to pick up resources without getting out of the suit.
  • In-Universe Game Clock: There's a day-night cycle which not only informs what creatures you'll see, but also how aggressive they'll act; most are bolder at night. Story progression is also partially determined by the passage of time. Case in point: the Aurora's reactor goes critical after seven days have passed.
  • In-Vehicle Invulnerability:
    • Played With in the opening cinematic. The player climbs into an escape pod and gets promptly knocked out by a piece of metal smacking them in the face. However they also end up being the only survivor of the Aurora crash.
    • Played straight by all vehicles, which have a separate health meter from the player. While running into things may damage your vehicle, you'll never be knocked unconscious by flying shrapnel like in the opening movie. The Cyclops was once immune to the attacks of creatures, even Reapers (who can destroy your Seamoth in two bites), but it now has a health bar like the others and can be damaged and destroyed if you're not careful.
    • And then subverted to hell and back by the Warpers, biomechanical menaces with the ability to teleport you out of your vehicle at will so they can attack you in melee. Extremely annoying no matter the circumstances, especially since Warper attacks are among the most powerful in the game, and those things are barely larger than a human. They can't do this when you're piloting a Cyclops, though.
  • Item Farming: Titanium and quartz in particular, because those are needed for bases and vehicles.
    • The primary function of the Alien Containment, which makes farming food, water and energy a breeze, freeing up time to truly begin your exploration of the ocean.
    • Players have come up with a trick for farming Stalker Teeth: approach Stalker territory and drop a handful of scrap metal pieces in the outer area. The closest Stalker will soon proceed to swim back and forth between the pieces, mostly ignoring the player while losing teeth regularly.
  • Jet Pack: A vehicle announced for possible inclusion after V1.0.
  • Jump Jet Pack: Built-in feature of the PRAWN suit. There's an upgrade to improve the jump too.
  • Kaiju: The infamous Leviathan-class lifeforms are gigantic, measuring between 55m (Reaper) and 200m (Sea Emperor) in length. It's probably not a coincidence that some of them bear more than a few similarities to the villainous monsters in Pacific Rim. Their database entries also lampshade that these monsters are rapidly approaching the size limit for sustainable organic lifeforms.
  • Killed Offscreen: At one point, the radio intercepts a piece of inter-Warper communication stating that there are nine Aurora survivors unaccounted for. Soon thereafter, another communique states that there's only one of them left (guess who), implying that the rest are being eliminated while you're doing whatever.
  • Kraken and Leviathan:
    • The PDA uses the term "Leviathan Class" to describe only the biggest biologically feasible fauna. Note that this is just a size classification, the Reefbacks and Sea Treaders are considered Leviathan Class.
    • On the other hand, if a species includes the word "Leviathan" in their actual name (e.g. Reaper Leviathan, Ghost Leviathan), it's probably best to run and don't look back.
    • One PDA entry indicates that the tremendous size of the Sea Emperor means they're going to have to recalibrate their size scale.
    • In the Lost River biome, players can come across a few multi-million year old skeletons. One in particular has jaws large enough to fit the Cyclops comfortably inside, giving the descriptor "leviathan" a real workout.
    • A “kraken” type creature is a frequent suggestion on forums and the game's subreddit.
  • Late to the Tragedy:
    • Seconds after the protagonist escapes the Aurora, they are knocked out cold by a panel that has gotten loose. By the time they wake up, all other people who made it off the ship have already perished. And that's to say nothing about what happened on Planet 4546B in the first place.
    • The presence of a meteor in the Dunes and some of the PDA's suggestions imply the Precursors qualify for this trope as well, and releasing the Kharaa only rubbed salt in the wound.
  • Lethal Lava Land: The Inactive Lava Zone and the Active Lava Zone.
  • Lightning Bruiser: Reaper Leviathans, full stop. They can swallow the player whole, can crack a Seamoth in two hits and players are physically incapable of outrunning them.
  • Lily-Pad Platform:
    • Presumed to be the case with the yet-to-be implemented Lilypad Biome.
    • Can actually be used in the Lost River biome with the rare Brine Lily.
  • Loading Screen: There's only one, when you're starting a new game or loading a saved game.
  • Loads and Loads of Loading: Unless you have a fast computer and very fast hard drive, you will be staring at that initial loading screen for several minutes.note . Thankfully the game switches to dynamic loading after that and you'll never see a loading screen ever again once you're in the game, unless you quit back to the title screen.

    M-Z 
  • Made of Iron: Most hostile fauna counts. It's extremely difficult to outright kill anything larger than a cat. Even the Prawn Suit's giant drill arm will merely chase off attacking predators like Bone Sharks for a short while; you can drill into one for a full minute or more without the beast dying, and that's next to impossible to pull off anyway without glitches because all predators are much faster than the Prawn. You need to get really creative if you want something dead.
  • Meaningful Name: Invoked, since your PDA is generating names for creatures as you encounter them, so almost all of them have names directly tied to their distinctive traits. In fact, the Reginald actually sticks out as being the only fauna that doesn't have such a name.
  • Mega Corp.: The 37 "trans-gov" corporations that control the galaxy. Two matter in the game: The Alterra Corporation that owns the Aurora and makes just about everything seen, and the Mongolian Empire that owns the Degasi. note 
  • Minimalist Cast: The player character is the sole human on the planet, and the other alien species there seem to be fairly normal animals in terms of intelligence.note  You can eventually find some old notes from previous crash survivors, but the state of their bases should be more than enough to tell you that they're long gone.
  • Mini-Mecha: The Pressure Re-Active Waterproof Nanosuit A.K.A. the PRAWN Suit, previously the Exosuit. It shares some upgrades with the Seamoth such as Pressure and Impact Compensation, but also has special arm variants that can be interchanged separately from the regular upgrades.
  • Mix-and-Match Critter: Some of the creatures have elements of two or more creatures. The Crabsquid is an octopus with Japanese Spider Crab legs and claws. The Sea Dragon Leviathan is a crocodilian with squid tentacles for its lower half, and the Emperor Leviathan is similar but with an insectoid/crustacean head.
  • Mood Whiplash: Appears in the soundtrack. Most of the songs are appropriately mellow for a game that predominantly takes place underwater, but upbeat, hardcore EDM plays whenever the Cyclops is critically damaged or goes up against a Leviathan-class predator.
  • More Predators Than Prey: The dev team works hard to avert this one: sure, there are some big, scary fish in the sea, but there are also lots of little, less scary fish.
  • More Teeth than the Osmond Family: Stalkers, but it's cool because you need the teeth and they've got an endless supply of them. Sand Sharks have several rows of teeth going down into their throats.
  • The Mothership: The Cyclops is a moderate, species-inverted example by virtue of being a player-controlled mobile base that also features an internal dock for carrying one smaller vehicle (Seamoth or Prawn, obviously).
  • Names to Run Away from Really Fast: Reaper and Ghost Leviathans, though by the time you get close enough to discover their names with the scanner, it's probably too late for that. Stalkers also count, although they're far from the most dangerous thing in the ocean.
  • Nature Is Not Nice: Most of the predators don't deliberately seek you out; you just happen to be snack-sized and in the vicinity. They'll just as happily eat small fish. Likewise, the greatest threat in survival mode isn't necessarily the wildlife itself; it's running out of food and water,note  or running out of oxygen while looking for resources.
  • No Biochemical Barriers: You're on an alien planet, but it just so happens to have a nitrogen-oxygen atmosphere and liquid water. Most of the sea life is edible, and those that aren't are specifically stated to be poisonous in order to avoid being eaten by larger species, rather than just being incompatible with a human digestive system. Of course, this is somewhat necessary for the game to be enjoyable to play,note  though it would be nice to imagine you at least give the Reapers indigestion after they eat you for the hundredth time.
  • No Body Left Behind: Despite having 157 people on board, not a single shred of a body can be found in the game. No blood splatters, no bones, no clothing scraps, no nothing. Meanwhile, several wrecks contain potted plants that got through the crash in one piece. Justified as the Warpers kidnapped and/or killed all of the survivors. And if it's the latter, their scythe-like arms are definitely sharp enough to avoid leaving behind tangible amounts of remains. Also, the PDA mentions that many indigineous lifeforms in and around the Aurora have trace elements of human tissue in their digestive tracts, so whatever remains did exist were simply eaten by the local fauna.
  • No-Sell:
    • Once a Reaper or Sea Dragon Leviathan has grabbed your vehicle, there's little you can do to make them let go. Shoot torpedoes into their face point-blank, grind the Prawn's giant drill into their forehead as much as you want, the beasts couldn't care less. Only one thing in the game can save your butt in this situation: the Seamoth's perimeter defense system, but unfortunately, the Seamoth isn't rated for the depths where Sea Dragons are encountered.
    • Ampeels and crabsquids are unaffected by the aforementioned Seamoth perimeter defense system, probably because they utilize electric attacks themselves.
    • The reinforced diving suit makes you immune to the Tiger Plant's spike bombardment, and the 50% damage reduction it provides on top of that enables you to tank a lot of attacks that would've nearly killed you otherwise. It also increases your temperature threshold before you take thermal damage to 70°C, which is sufficient protection to swim around even in the Lava Lakes with impunity as long as you don't get too close to the actual lava.
  • Notice This: Important stuff like databoxes and PDAs glows brightly in the dark, which makes them easy to spot even from long distances. It also makes it advisable to switch off your flashlight at least once per room while you're exploring wrecks so you don't miss them because your light overpowered theirs. Scannable fragments that unlock new blueprints tend to be a bit less obvious, but they do stick out from among the worthless rubble once you know what to look out for, and they also trigger a small scanner icon in the lower right corner of the screen when you enter their rough vicinity to alert you to their presence (helpful in wrecks because the fragments often blend in very well with the walls and floors).
  • Not the Intended Use: The Picture Frame is meant for pictures taken in-game. However, since those pictures are stored in a folder, it is possible to take any image that you want, place it in the folder, and then have the game treat it as another in-game picture. This can be used for an extra level of base customization, but the most popular use is to upload a user-made map because the game has no map system of its own.
  • Nothing Is Scarier: The Dunes and the Mountains biomes. Once you transition there, the music stops and all ambient noise goes quiet, save for the player's. All the better to hear the distant screams of Reapers.
    • It's even worse in the Void - no music, no fish, no sounds, no sea floor. Just endless ocean and inky darkness all around you. And then the Ghost Leviathans show up.
  • Ocean Punk: It's a mostly underwater survival game.
  • Oh, Crap!: The traditional reaction to a player hearing any of the distinctive roars that signal an imminent encounter with any of the three aggressive Leviathan species.
    • Also the likely reaction of a player being in position to witness the demise of the Sunbeam for the first time. It's proposed landing site is right outside the Quarantine Enforcement Platform, which resembles a curious alien tower when idle. Right before the hapless ship enters the atmosphere, the Platform begins to emit an alarm and starts changing shape. Before too long, the player will realize it's beginning to resemble a colossal gun turret. One that is now tracking the approaching Sunbeam...
  • One-Gender Race: The PDA mentions that all life on Planet 4546B is only one sex, they do not reproduce asexually though as each individual can both carry and fertilize eggs.
  • One-Hit Kill:
    • The Reaper Leviathan will grab you with its giant pincers, roar, and swallow you whole if you're under 80 health and outside a vehicle. Speaking of which, it can grab Seamoths and PRAWN suits and throw them against the ocean floor, destroying them in one hit.
    • The Sea Dragon Leviathan can eat you alive. It is exactly as terrifying as it sounds, and ten times worse if you witness it while playing in VR.
    • The Quarantine Enforcement Platform, AKA the cool-looking alien structure where the Sunbeam is scheduled to pick you up for evacuation, is actually a giant anti-orbit weapons platform that does this to any ship that enters its firing range. It brought down the Aurora in one shot and does the same to the Sunbeam, only the latter explodes right away without even a chance of performing an emergency landing.
  • Our Dragons Are Different: The Sea Dragon. It has a reasonable upper body of an aquatic dragon, plus squid legs.
  • Our Fairies Are Different: Rockgrubs are basically aquatic fireflies.
  • Oxygenated Underwater Bubbles: Either naturally when produced by Purple Brain Coral or manmade when produced by a pipe system.
  • Oxygen Meter: Unaided, you can hold your breath for 45 seconds, and going below 100 meters without a Rebreather cuts that time in half. You can get tanks which will add to your air, but you can still run out if you're outside of a powered vehicle or station. If you lose power, you'll soon lose air there, too. Running out won't immediately kill you, though; you'll begin to black out when your meter runs down, and if you manage to get a gulp of air before completely losing consciousness, it'll revive you.
  • Palette Swap: There are currently five creatures that are a texture swap of other creatures: Crimson Rays to Ghostrays, Blighters to Biters, Spinefishes to Hoopfishes, Lava Boomerangs to Boomerangs, and Lava Eyeyes to Eyeyes. The game also includes a few models that are not texture swaps but still very close in appearance to other models, such as Jellyrays and Ghostrays and Blood Crawlers and Cave Crawlers. Creatures part of the design repeats are explained to be genetically related.
  • Patchwork Map: Complete with Law of Cartographical Elegance.
  • Percussive Maintenance: When trying to free themselves from the chair in the beginning, the protagonist presses the button several times to no avail. So he slams his fist down hard on the panel, which naturally works.
  • Piranha Problem: Biters, which hunt in small schools and chase you from further away if your health is low.
  • Portal Network:
    • The reason why the Aurora was near 4546B was because it had visited the system to construct a phasegate here (though given no-one mentions going into cryosleep or anything of the like, it seems more "conventional" FTL travel is also a thing).
    • The precursors have created an entire network of portals on the planet's surface, connecting both islands as well as various facilities. By the time you arrive, they are shut down to stop the Kharaa from spreading - although they can be restarted from the Primary Containment Facility. The PDA describes them as miniature phasegates.
  • Power Crystal: Ion Crystals, used to activate alien portals and craft certain alien artifacts.
    • Also, to a lesser extent, Kyanite crystals, which are used in crafting some of the most powerful vehicle upgrades. Kyanite is a real material with industrial use that is indeed highly heat resistant. While not "powerful" in the mystical sense, they certainly do make some of your stuff more powerful.
  • Powered Armor: The reinforced diving suit and the PRAWN qualify - the latter especially, as in addition to making you very tough to kill, it provides an infinite supply of oxygen, increases your speed. Also, if you mount the grappling hook, it allows you to move around much faster than swimming with just fins. The PDA even warns you against going on a power trip the first time you use it.
  • Precision F-Strike:
    • In a log file on the Habitat Update's webpage.
    Controller: (responding to the Aurora’s survival PDAs running version 1.0) Bring me every star chart, tech geek and concentration enhancer in the building...
    Analyst: Yes Ma’am!
    Controller: ...and god DAMN it you build me an update package, and you find me a way to flash them Version 1.1!
    • And later this on the Seamoth Update's webpage.
    Controller: Ship [the survivors] the Defense System and the Vortex Torpedoes.
    Analyst: But ma'am, weapon designs violate directive 7!
    Controller: Directive 7 is there to eliminate the risk of survivors turning on one another. If they're going fin-to-fin with alien krakens then they have bigger fish to fry. I want them prepared, and damn the directives!
  • Primal Fear: You're in the depths of the ocean on an alien planet. Nothing is familiar; the shilouettes in the distance could be harmless or deadly, and you're never given any reliable weapons with which to fight back against the unknown. In the pitch-black night, you'll never know for sure if anything is sneaking up behind you for a quick bite...
  • Pure Energy: Any power source built outside (and power transmitters) transmit the energy to the nearest base not by cables, but by a beam of sorts.
  • Reality Ensues: A humorous example. When Ryley finally deactivates the Quarantine Enforcement Platform and gets stabbed in the arm again, he reacts by punching the console in anger. Being basically a massive slab of metal, the only result is him bruising his hand.
  • Recoil Boost: In a non-weaponized example, spraying the fire extinguisher underwater will cause you to move backwards. Slowly, yes, but it can be a fun distraction. Above water (i.e. in your base or the Aurora), there's naturally no recoil, as your feet are firmly planted.
  • Regenerating Health: Your health recovers slowly but surely.
  • Respawning Enemies: The creatures of Planet 4546B eventually respawn. As of the full release, however, medium to large creatures no longer respawn, meaning it is possible to Kill 'em All. Yes, this includes most Leviathans.
  • Retractable Weapon: How the Quarantine Enforcement Platform innocuously disguises an energy weapon capable of felling a flying city like the Aurora in a single shot.
  • Ribcage Ridge: The Bones Field in the Lost River area contains a large, dragon-like skeleton. A couple of smaller versions of the same skull and bones have been added as well, and the skeletons of Reaper Leviathans and Sea Dragon Leviathans will be added in the future. It's basically the undersea equivalent of an Elephant Grave Yard, and there is Truth in Television, as underwater cavern systems can trap animals that go into them.
  • Ridiculously Fast Construction: Alterra's fabricator technology can construct virtually anything in a matter of seconds, assuming the user provides the blueprints and the required materials. It can even build the Neptune, a huge single-stage interorbital rocket, in less than three minutes.
  • Robo Speak: Averted by the AIs that manage your bases and vehicles, but played straight by the escape pods' automated distress signal transponders.
  • Salt Solution:
    • Salt is needed to conserve dead fish or they'll go bad very quickly. It is also used as an ingredient to create bleach for disinfecting water, and it's needed for a number of vehicle upgrades.
    • Salt can also prove hazardous to your health. The brine rivers and lakes in the Lost River biome are so highly concentrated that touching them is akin to getting doused in acid, dealing high damage in very short ticks.
  • Scenery Gorn: In marked contrast to the unbelievably gorgeous rest of the game world, the Crash Zone looks more like Mordor than anything else. The radiation leaking from the Aurora's ruptured reactors has turned this huge area into a brownish wasteland almost entirely devoid of plant life, but hey, at least you've got eight Reaper Leviathans keeping you company.
  • Scenery Porn: The game's main selling point - the designers worked very meticulously to invoke this trope, and the result truly must be seen to be believed.
  • Schrödinger's Gun: Depending on when you cure the Kharaa, there's a sufficiently dense debris field that prevents the Sunbeam from rescuing you.
  • Scripted Event: Radio messages and PDA log files. The explosion of the Aurora and the Sunbeam being shot out of the sky both qualify as a Video Game Setpiece.
  • Sea Monster: Plenty fulfill the classic tropes — giant squids, Krakens, and Leviathans galore, in addition to exotic but "normal-sized" sharks. The Crater's Edge (formerly known as the Void) surrounding the playzone used to host an onslaught of dangerous fauna to discourage players from venturing too far without resorting to an Invisible Wall or Wrap Around, but as of the full release the game jumps directly to spawning adult Ghost Leviathans to chase the player until they escape the area and cause them to despawn.
  • Send in the Search Team: What the Aurora is to the Degasi and the Sunbeam to the Aurora.
  • Sequence Breaking: Nothing forces you to repair the radio in Lifepod 5, and it's entirely possible to play through the game without the numerous hints you normally get by listening to the frequent radio calls. However, doing so results in missing several key events and important plot points, like the Sunbeam getting shot down by the Quarantine Enforcement Platform, or receiving the code for the Aurora cabin containing the Neptune blueprints. Once you repair the radio or build a new one, all the messages you missed will still be received one after the other, only with a lot less context and even less actual use to you.
  • Shared Universe: With Natural Selection 2, also made by Unknown Worlds. Originally the name of the Alterra corporation on the Knife's blade was considered merely an easter egg, until a log file coded with a Caesar cipher and ASCII on the Habitat Update’s promotional webpage mentions “the Kharaa conflict," and as the game's wiki notes, the Kharaa are, in fact, connected with the Kharaa Bacterium in some fashion. note 
  • Shock and Awe:
    • The Ampeel uses this, similar to a real-life electric eel.
    • The Seamoth's Perimeter Defense upgrade, which is more realistic.
  • Shown Their Work: Before lead became a resource to find as any other (Machinery update), it was manufactured by combining copper and silver ores. This reflects the fact that lead can be found in ores of other metals, such as Galena (an ore of silver). However, for a while lead used to be manufactured from two batteries.
  • Sickly Green Glow: The Lost River biome is defined by highly concentrated brine rivers that, probably thanks to the Rule of Cool, glow an eerie green. Like most video game liquids that look like this, the brine even acts much like acid when you touch it, but at least it's not radioactive.
  • Single-Biome Planet: Thoroughly averted; the underwater world has rich and diverse areas, varying not only by location but also by depth.
    • In the game's ending the planet is also shown to have a number of large islands and polar ice caps, the latter of which is planned to be the setting for an expansion pack.
  • Sinister Geometry: It's debatable how evil the precursors really are, but their buildings sure look plenty sinister. Everything's assembled from cubes of various sizes, the material is some black, nearly indestructible alloy covered in green Tron Lines, and the architecture itself is oppressive, monolithic and strangely reminiscent of temples/shrines even though the facilities the player visits are exclusively scientific or military in nature.
  • Solid Gold Poop: What Sea Treaders drop. It's only useful as biofuel right now but is expected to be crucial to farming later in development.
  • Something Completely Different: The entire game takes place in the ocean, except for your life pod, the crashed Aurora, a floating island, a true island, and a Lilypad Biome yet to be implemented.
  • Sound-Coded for Your Convenience: All the wildlife is quite noisy, and makes unique sounds to boot. Learning which creatures make which sounds lets you know when it's just a big Reefback saying hi and when you're about to be eaten alive.
  • Space Is an Ocean: The Seamoth mini-sub is classified as a "one-person sea-and-space vehicle". Sadly, the player doesn't get a chance to put the "space" part to the test, but at least it handles marvelously underwater.
  • Space Isolation Horror: The game leaves you stranded on an ocean planet full of large, terrifying sea monsters who want to eat you.
  • Spike Shooter: The Tiger Plant, which you can also grow yourself.note 
  • Sprint Shoes: The basic underwater variant are a pair of silicone flippers, which slightly increase the player character's baseline swimming speed and can be upgraded into Ultra Glide Fins. The straighter variant though is the Seaglide, which is a fancy DPV, or a propeller with handles. It comes with a local topography map and flashlight. It's also able to be recharged indefinitely with Swim Charge Fins (which may or may not change in future updates), but only when the topo map and flashlight are switched off.
  • Standard Status Effects: Played with. When in contact with Drooping Stingers or the Gas Pods from Gasopods, the health bar dwindles rapidly due to poisoning. Escaping the contact will return all the health lost.
  • Stat Death: Running out of oxygen won't do anything to your health bar, but you'll die anyway if you don't reach an oxygen-rich environment soon.
  • Sub Story: The Cyclops in particular. Silent Running Mode is coming up.
  • Super-Persistent Predator: Largely averted. Most predators will tend to avoid the player character unless an opportunity presents itself, and even then will tend to give up the chase if the player character can outrun them or proves themselves capable of hurting the predator (a good knife wound will often send the predator swimming away as fast as its fins can propel it.) On the whole, they tend to prefer easy prey. The closest thing that comes to playing this straight are the Reaper Leviathans, which seem to be apex predators. If one spots you, run. Run and don't look back. Or, seeing as it can outrun your Seamoth and also tear it to shreds in seconds, don't bother.
    • That said, the Seamoth Perimeter Defense system allows you a quick zap to minimize hull damage that will send Reapers the other way, or a longer charged-up one that can outright kill smaller predators (including bone sharks). However, Reaper, Ghost and Sea Dragon Leviathans won't be discouraged for long by the shock.
    • They also won't be distracted for long by Creature Decoys which can be hand dropped or launched by the Cyclops. Hell, even being scooped up in a PRAWN suit and using the drill arm(s) to fight back won't make a Reaper let go of you, to say nothing of the other two mean beasties.
    • The single most reliable way to evade them is judicious application of a Stasis rifle or a Vortex torpedo, which are capable of paralyzing a Leviathan for several precious seconds while you try to flee.
  • Swallowed Whole: What happens after the aforementioned Reaper Leviathan catches you. Also one of the ways the Sea Dragon Leviathan can seal your doom, if it doesn't roast you with its fire breath.
  • The Symbiote: The Crashfish and the Crashfish Plant as well as the Crabsnake and the Jellyshroom.
  • Take Your Time: The game very heavily implies that you will die after about five weeks, thanks to exposure to the Kharaa bacterium and that symptoms should start appearing around two weeks in. Instead, the disease's progression is entirely event-based, and the player will never fatally succumb to it. Slightly justified, thanks to the presence of Peepers spreading diluted Enzyme 42, which inhibits the bacterium's growth and progression. For the same reason the Kharaa hasn't wiped out the entire biosphere, it's possible Ryley is kept alive via indirect exposure.
  • Ten-Second Flashlight: Downplayed with the hand flashlight, which lasts a fairly long time on a full battery, but not nearly as long as one would expect with all the other high-tech gizmos those batteries can run. Vehicle lights come in two flavors: the Seamoth and Seaglide have a small drain when the lights are on, while the PRAWN and Cyclops provide light for free.
  • This Is a Drill: An exceedingly useful modification for the PRAWN is a huge drill arm; specifically, a grinder-style drill, intended to pulverize mineral deposits for harvesting rather than tunnel through the ground. Unsurprisingly, it also makes for a pretty decent melee weapon in a pinch. Seeing how constructing it consumes a large amount of diamonds, the blades are most likely diamond-tipped.
  • Threatening Shark: The Stalkers (during development also known as Snout Sharks), Bone Sharks, and Sand Sharks.
  • Unbroken First-Person Perspective: The closest to a break is when you control one of the Camera Drones and can see yourself at the console if you have a well-placed window. But even then what you see with the camera is what the character sees on the console.
  • Unexpectedly Realistic Gameplay:
    • It's not obvious from the start that oxygen tanks actually store oxygen rather than merely increasing your cap. If you have several in your inventory, each has its own supply and can be swapped out as the equipped one depletes. Similarly, each individual tank must be refilled with air by equipping them.
    • Also applies to the game as a whole. The vast majority of contemporary survival games have tutorials, quests, map markers (not to mention a map in the first place), a more or less strict narrative with a clear ultimate goal, and so on. Subnautica's total lack of any hand-holding can be baffling to new players until they switch their standard video-gaming expectations back to common sense and think about what anyone who's stranded in uncharted territory would do: survive the first day, come up with a plan to get the hell out of there, and then survive long enough to figure out how to do just that.
  • Under the Sea: Almost the entire game takes place in the ocean, with a couple of islands and the non-submerged half of the Aurora being the only exceptions.
  • Underwater Base: You can make these using the Habitat Builder and raw materials such as titanium and glass.
  • Unstable Equilibrium: The beginning of the game is almost exclusively about basic survival: getting food and water to stay alive long enough to get equipment to survive the planet's dangers. Obtaining the means to farm your food is a huge step in freeing up time to spend on exploration, but certainly isn't the only boost forward.
  • Unwinnable by Mistake: There are a number of ways to get yourself stuck in the deep sea with no way to continue the game, exacerbated by there only being one single savegame per campaign and no autosaves.
    • If you die and aren't playing on Hardcore, you're warped back to the last habitat you visited. If that death also involved the destruction of your vehicle, and your last habitat happens to be situated too deep to reach the surface by swimming, you're screwed.
    • It's quite easy to underestimate the time it can take to navigate the game's labyrinthine tunnel systems. Fail to pack enough spare power cells for your vehicle, or enough batteries for your repair tool, and you can find yourself in the same situation as above very suddenly. The loss of your vehicle at great depths in general is an almost certain death sentence even if you initially survived its destruction.
    • You may also simply die of thirst or starvation on such excursions. The latter can usually be staved off by catching some edible fish, but eating them raw seriously lowers your hydration meter, so you're dead anyway. Always make sure you have a healthy supply of food and especially water before you head out.
    • Until you reach the Primary Containment Facility, ion cubes are a strictly limited resource with only a handful of samples to be found in the game world. If you spend too many of them building the wrong stuff, you may lock yourself out of the final levels, making it impossible to finish the game.
  • Villain Teleportation: Well, Threatening Force Teleportation, anyway. Warpers are cyborgs with built-in teleportation hardware. They can come and go as they please. Not only that, but they can teleport you out of your vehicle so they can attack you directly, and warp hostile fauna in on top of you.
  • Violation of Common Sense:
    • The Prawn Suit's grappling hook is meant for helping it traverse vertical distances easily and quickly, but despite the "magnetic" part in its description it can latch on to almost anything. Even Leviathans. There's no benefit in doing so, considering the beast can still fully attack the Prawn, except for the sheer badass factor of playing rodeo with a 50-meters murder machine.
    • In a similar vein, Leviathans can be scanned like any other creature. Needless to say that attempting this is extremely dangerous, very likely to get you killed, and ultimately useless because creature scans don't actually do anything beneficial. At least your PDA lampshades it by congratulating you in case you do manage to pull it off.
    • Ion cubes are strange, glowy green artificial crystals the size of a human head that contain as much energy as a tactical nuclear warhead each. Like most mineral-like resources, ion cubes may be found in large deposits, which you can mine by shoving a huge honkin' Prawn grinder drill into the ominously glowing six-foot cluster. Nothing bad happens, but man, there's gotta be a more subtle approach to this sort of business.
  • Volcano Lair: The Lava Castle, a massive castle-like rock formation located deep within the Inactive Lava Zone. It's home to the Precursors, along with the Active Lava Zone directly below it. All of their power comes from the Lava Castle, and is budgeted into various operations.
  • Walk, Don't Swim: As far as creatures go, Cave Crawlers, Blood Crawlers, and Sea Treaders. The player is capable of this too when controlling the PRAWN suit.
  • Weapon of Mass Destruction: The ion crystals you find all have the power of a thermonuclear detonation. Subverted in that they are so stable that you would have to take a lot of steps to set them off.
    • Yet this is played very straight with a small grenade sized weapon you can find in the final Precursor base. Apparently made by a different precursor species and put on display here, it's energy potential isn't just enough to wipe out the base or the entirely of the local biomes, but the entire planet to boot.
  • We Hardly Knew Ye: Every single human and the precursors qualify, but Captain Avery Quinn takes the cake.
  • Well-Intentioned Extremist: The Precursors. They were the ones responsible for shooting down the Aurora and Degasi, and later the Sunbeam that lands to try and rescue you in front of your own eyes. However, there's a reason they're doing all of this. A bacterial epidemic ravages the planet, which has infected enough creatures to become the norm. The Precursors want to cleanse the planet of the bacterium... by killing all those with it. In desperation, they built the surface-to-orbit oversized cannon, euphemistically called the Quarantine Enforcement Platform, and wound up killing a bunch of Sea Emperors - note the plural; 314 to be exact - trying to find a cure. They also created the Warpers.
  • The Worf Effect: Reaper Leviathans are highly dangerous early in the game. In and around The Lava Zones are Reaper skeletons that the Sea Dragon left behind after eating them.
  • Worthless Yellow Rocks: Played with. Gold is one of the two resources that play a special sound every time you pick a piece up. It is also the only resource found in three of the five available harvest nodes (Sandstone, Basalt and Shale). While there are some uses for gold, its first two harvest node colleagues, silver and lithium, are more sought after as they're used in recipes more crucial to survival. Explanation  Averted in the Silent Running update, which changed the recipe for the Computer Chip to accept Gold instead of Silver.
  • Yank the Dog's Chain: After everything the survivor goes through, from scavenging for food and water, to fending off giant predators, to curing a disease that has plagued the planet for over a thousand years, he finally builds a rocket and escapes, only for Alterra to claim that he owes them one trillion credits for all the resources he scavenged, and they won't grant him permission to land until he pays it. Hope you can barter off all the information gathered from scanning the items in 4546B, as well as brought Precursor tech back to barter off, and even that might not work, since Alterra preemptively claimed everything on the planet was their property to begin with.
  • You Shouldn't Know This Already: Mostly averted due to the game's open world and non-linear plot progression.
    • Code-locked doors always require the same passcode to unlock, and if you happen to know the combination from a guide or a previous playthrough, you can open them without having found the information in-game before.
    • You can investigate plot-critical locations and perform plot-critical tasks without having been given the order via radio or PDA. The story doesn't have a truly fixed linear narrative, so you can complete its objectives in almost any order, although several of them still require specific equipment to become accessible. Knowing the entrance to the Active Lava Zone won't help you much without a heavily upgraded Prawn or Cyclops to actually get you there.
    • While fragments of basic gear like the Seaglide, the laser cutter, beacons and so on are semi-randomly distributed across the minor wrecks, the large ones always provide the same salvage, and important stuff like Prawn or Cyclops parts can always be found at the exact same locations. You know the spots? Go and get 'em at any time.


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