[[quoteright:256:http://static.tvtropes.org/pmwiki/pub/images/Endless_Ocean_Coverart.png]]
[[caption-width-right:256:Dive in.]]

''Endless Ocean'' is a WideOpenSandbox AdventureGame mixed with a scuba diving sim by Arika, which simulates a series of scuba dives on an incredibly diverse coral reef. It became legendary for completely eschewing combat of any kind.

You, the player character, are a professional diver assigned as a "marine correspondent" to the fictional South Pacific island of Manoa Lai (Manaurai in the European release). This job generally involves looking at a lot of fish, and finding out information about them. The only character you actually get to interact with is your marine biologist assistant, Katherine. Along the way, you discover ancient ruins, caves, deep waters, and lots of MisplacedWildlife (though they at least made them all real fish).

There's a sequel entitled ''Endless Ocean 2: Adventures of the Deep'' (known as ''Blue World'' in the US), which allows players to choose from several dive spots around the world instead of being limited to a fictional South Pacific Ocean, including [[SlippySlideyIceWorld the arctic and antarctic]] and a [[BubblegloopSwamp section in the Amazon River]]. Dangerous animals can now actually attack the player, requiring the divers to make a quick escape or use equipment to pacify them before becoming [[strike:alligator]] caiman, piranha, or shark food.

Not to be confused with ''The Infinite Ocean'', a fairly creepy point-and-click adventure game about the first ArtificialIntelligence. Compare ''VideoGame/{{Abzu}}'' for the UsefulNotes/PlayStation4 and Steam.

Both games have been played by the WebVideo/GameGrumps, giving them considerably more exposure.
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!!This game provides examples of:
* AbsurdlyHighStakesGame: Jean-Eric won Nineball Island through the billiards game it's named for. In other words, he's a [[{{Pun}} pool shark.]]
* AcceptableBreaksFromReality: Many aspects of the game's diving are dangerous in real life, but the game would be frustrating to play if the dangers were played straight.
** Normally diving hours are restricted. Divers are forced to use tables to calculate the amount of hours they can safely dive on a day, depending on the depth and time they already spend underwater. None of the characters follow these rules; in RealLife they would all get serious illnesses.
** With the exception of a few plot-related sequences, you can always go back to the boat, no matter the circumstances; even when on threshold of running out of air, surrounded by aggressive creatures, or underground. Real-life divers cannot take that kind of liberty with their air, especially as surfacing too quickly has its own problems.
* AllInARow: How your diving partners follow you. In the original game, you could make fish follow you by petting them a bunch of times after you've already learned all the facts about their species.
* AmazingFreakingGrace: One of the songs in the original.
* [[AnInteriorDesignerIsYou An Island Decorator Is You]]: ''Blue World'' lets you spruce up Nineball Island with various pieces of furniture, as well as stock a nearby reef with corals and kelp. You can even gain titles by getting all the pieces.
* AndYourRewardIsClothes: You frequently get new wetsuits, hairstyles, and scuba tanks as gifts from guided tour patrons or photography editors.
* ArbitraryHeadcountLimit: You can only have three dolphin partners in the first game; befriending a new one beyond that will force you to kick one of them out. They're not lost forever if you change your mind, though.
* ArtMajorBiology: Largely averted, though it does crop up here and there. Greenland sharks are very slow swimmers and have never been known to prey on humans (though considering where they live this could be due to the two species almost never meeting), and goblin sharks don't have their jaws extended at all times, to name two examples.
* {{Atlantis}}: Mo'ia Atoll, [[MaybeMagicMaybeMundane maybe]]. Okeanides in ''Blue World''.
* AwesomeYetImpractical: In the first game, dolphin partners were cool and all, but had no real use - they tended not to follow you very well unless you blew the whistle every few yards (and took forever to come to you from across an area if you let them alone for a while before calling them), and riding them was neat, but couldn't be controlled, so you just go to watch yourself go in circles until you let go. They were made much more useful in the sequel.
* TheBeastmaster: The PlayerCharacter is this. In the first game no animal will attack you, not even sharks, and small fish will actually tag along with you if you play your whistle near them. While sharks become aggressive in the second game, cetaceans seem to respond to you much more favorably [[spoiler:just like they did for the ancient Okenaides people]] and several will help you if you befriend them.
** [[spoiler: The Okenaides and the Mo'ia Atoll people could control cetaceans through songs, and formed the first world-wide civilization with their help.]]
* BadassCrew: While not in the traditional sense of the trope, in terms of diving expertise the second game's FiveManBand is perhaps the best in the world. Consisting of a retired adventurer with more years of experience then the rest of the crew put together, one of the world's leading marine biologists, a world renown salvage expert, and two life long pro-drivers one of which has abilities that are nearly super human.
* BigCreepyCrawlies: [[spoiler: The Grave Keeper is about twice the size of its already enormous friends.]]
* BigFancyCastle: Valka Castle is a rare underwater example.
* BlackoutBasement: Both games' abyssal zones, lit by nothing but your portable flashlight. Hugging the sea floor is almost a requirement just to keep your orientation.
* BraggingRightsReward: The legendary creatures in ''Blue World''. Many of them are only found in a single area that is either difficult to reach [[spoiler:for example, the giant sturgeon Lady Dorothea/Divine Gift is at a wreck surrounded by great white sharks]], or requires a specific diving partner/time of day/moon phase/item. Or they might just be tough to handle (half the time, you're too busy running away from [[spoiler:Thanatos]] to photograph him). Finding any particular creature earns you a title.
* ButThouMust: In ''Blue World'', after you and Oceana find [[spoiler:the plesiosaur]], Oceana decides she's not going to publicize this discovery, and asks if you agree. You can say "I do" or "No I don't," but if you pick no, Oceana will just say "Really?" and ask you the question again. And again. And again.
* CaptainErsatz: Leviathan from the second game - an albino sperm whale with a reputation for attacking ships, with a fanatical captain hunting him down in to get revenge. [[Literature/MobyDick Sound familiar?]]
* CartographySidequest
* TheCatfish: [[spoiler:Magu Tapah and the Ancient Mother]] in the first game; ''Blue World'' has '''many''', including an actual catfish that has [[AmazingTechnicolorWildlife turned golden in color]].
* CelebrityPower: Notable New Zealand vocalist Music/HayleyWestenra provided nearly the entire soundtrack for the game; her song "[[http://www.youtube.com/watch?v=dvuZ9j9gzlQ Prayer]]" was used for early demo display purposes, as well as being the [[RealSongThemeTune unofficial theme]] for the final product. The group Music/CelticWoman provides some songs for ''Blue World''.
* ChuckCunninghamSyndrome: Ichiro Enoshima/Ken Kaimoto from ''Blue World'', who has an introduction that makes him seem fairly important before he disappears from the rest of the game. It seems that he was originally planned to have a much larger role, but Hayako apparently took most of it over.
* ContinuityNod: ''Blue World'''s notebook mentions, in the entry about the Pelago Commonwealth, that [[spoiler:a new species of whale]] was discovered in the Manoa Lai region two years ago; two years separated the releases of the first and second games. It's also mentioned in passing that Hayako helped [[spoiler:catch and release a giant whale.]]
** Also, Nancy sometimes mentions that she wishes she could send you her stuff via e-mail; this is the manner in which ''everything'' was received in the first game, despite the impossibility (such as a wetsuit being sent as an e-mail attachment).
* CoolBoat: The ''Gabbiano'' in the first game, which the loading screens are quick to remind you is Italian for "seagull".
* CosmeticAward: "Titles" in ''Blue World''.
** Earning enough titles earns you the Poseidon diving gear. Includes a mini whale shark as an air tank for extra awesomeness!
* DerelictGraveyard: The Ship's Rest area in the first game and most of Ciceros Strait in the second.
* DisneyDeath: Oceana's father was mentioned to be dead from attempting to explore the Zahaab Region Depths for the Okeanos Temple. However, a certain sidequest implies that he survived, but lost his memory for a good part of the game.
* DubNameChange: Several locations and legendary creatures have different names in the American and European releases. For example, the legendary giant sturgeon is named "Lady Dorothea" in the American release and "Divine Gift" in the European release.
* EnemyScan: Using your ''hand'' to fill the Marine Encyclopedia.
* EverythingsBetterWithPenguins: All over the [[SlippySlideyIceWorld Weddell Sea]] in ''Blue World''. There's two legendary penguins hanging around: Big Bobby, a human-size emperor penguin, and Snowball, an albino rockhopper penguin. Both appear only during certain weather conditions; Big Bobby is only found in clear weather, and Snowball is only found during snowstorms (making her harder to see).
* EverythingsSquishierWithCephalopods: GiantSquid enjoy the abyssal trench areas in both games, and there's the stock smaller variety and octopi, too.
* FakeLongevity: In the first game, you had to find each creature on three separate days in order to learn all three sets of facts about them to complete the Marine Encyclopedia. ''Blue World'' shortens this down to everything being learnable in a single encounter, but also introduces money that has to be earned through work to spend on new gear. [[spoiler:Not to mention saving up ''a million'' pelagos in order to open Okeanides back up to casual exploration.]]
* FanService: [[DownplayedTrope Downplayed]]. If you purchase swimwear in ''Blue World'' that doesn't consist of a wetsuit and have your character wear it, you can have him/her partake in a ShowerScene using the facilities behind the Nineball Island cabin.
** Or, if you don't need your character to be washing to appreciate it, you can take your character on a dive in the swimwear. Then you can go ashore, and look all around. Or hey, if the front is all you need, looking at the character wearing it in the equipment menu is sufficient.
* FastForwardMechanic: A location is provided to allow the player to move rapidly to another time of day and forwards in time with regards to things like missions.
* FinalBoss: Surprisingly, ''Blue World'' has one: [[spoiler:a huge goblin shark called the Okeanos Guardian, with [[FlunkyBoss a pair of goblin shark cronies at his disposal]]. In addition to the usual shark TailSlap, the Okeanos Guardian can also reactivate the traps in the BossRoom, forcing you to restart the room's puzzle.]]
* FireForgedFriends: The crew in the second game may start out as just business and research partners (not counting Jean-Eric and Oceana), but they definitely end up as this by the end.
* FiveManBand: In the second game.
** TheHero: You
** TheLancer: Oceana
** [[TheSmartGuy The Smart Chick]]: Hayako
** TheBigGuy: GG
** [[TheChick The Dude]]: Jean-Eric. Also TheMentor, though he remains a NonActionGuy due to an [[CareerEndingInjury illness that keeps him from diving]].
* {{Foreshadowing}}: The [[spoiler:Ancient Mother]] is foreshadowed by such things as the skeleton at the bottom of the Abyss, and Kat's comments when you assemble the Whale God Mirror. Mo'ia Atoll is also mentioned in passing during the Great Aqua Cave's backstory.
* ForScience: It is implied in the [[spoiler:''Anomalocaris'']] article/trivia that the one that GG and the player character encountered at Valka Castle was revived in a genetic experiment, and somehow was released into the wild.
* FriendlyPlayfulDolphin: The games naturally feature dolphins and larger cetaceans from various locations. You can befriend certain dolphins. When players get to nineball island in ''Endless Ocean Blue World'' they can teach tricks to a dolphin.
* GaiasVengeance: Thanatos' trivia wonders if his emergence is Mother Nature's revenge for humanity's DisproportionateRetribution against shark attacks.
* GenkiGirl: Oceana, at times.
* GhostShip: The large brown vessel which transports you to and from Ship's Rest, which you enter via ''the big gaping hole in its hull below the water line.'' In Ship's Rest itself, you can see the wreckage of the exact same boat right in the sand below where it's floating. It's actually really eerie, especially at night.
* GiantSwimmer: You can ride whales and dolphins through the ocean, though you can't control where they go. In ''Blue World'', your dolphin partner ''can'' follow your directions, which is necessary in the freezing regions until your equipment improves.
* TheGoomba: Bicolor parrotfish are a nonviolent version of this. They appear practically everywhere.
* GreenAesop: Rears its head more often (close to {{Anvilicious}} levels) in the sequel than the original, but present either way.
* GuideDangIt: Getting OneHundredPercentCompletion in these games can be a nightmare without a walkthrough, given how large the areas are, coupled with the first game's penchant for [[RandomEncounter randomizing item/fish locations]]. Unlocking the missions to recruit more cetacean partners in the second game isn't immediately obvious, either.
* HeroicAlbino: [[spoiler:The Ancient Mother in both games and the Singing Dragons in ''Blue World''.]]
** ''Blue World'' is ''obsessed'' with albinos. A good chunk of the legendary creatures are albino, as is the bottlenose dolphin partner.
* HeroicMime: The player character.
* HotScientist: Kat and Hayako.
* HouseboatHero: The first game.
* HowWeGotHere: ''Blue World'' opens on the player character interacting with several "strangers" and being guided towards a massive underwater ruin...and then the backstory kicks in for the rest of the game.
* HumansAreTheRealMonsters: In ''Blue World'', [[MaddenIntoMisanthropy this becomes Oceana's philosophy]] by the midway point of the "Help Me!" sidequests. She forgives humanity after the final quest in the set after helping keep some whales from breaching.
* ImplacableMan: Or shark, rather. Thanatos is completely immune to the pulsar gun, and he will not stop attacking until you leave his turf. Exploring his territory in Ciceros Strait is a royal pain.
* InUniverseCamera: When in third-person mode, any kelp, small fish, etc. pushed aside by the camera are actually due to Kat's "unmanned, remote-controlled minisub" following you.
* InUniverseGameClock: Different creatures can appear depending on when you dive. Furthermore, the first game actually cycles through a whole year which further alters what you can find, as animals enter and leave Manoa Lai depending on the seasons. ''Blue World'' adds phases of the moon to the mix.
* LastLousyPoint: The Yatabai Blenny is legendarily hard to find.
* LuckBasedMission: Anything involving a zoom-in point which doesn't [[NoticeThis shine beforehand]] in the first game. This includes a number of the smaller creatures and roughly half of the salvage items.
* LyricalDissonance: The title screen theme for ''Blue World'', [[https://m.youtube.com/watch?v=IijKg8p3LMs Carrickfergus]], is a beautiful, peaceful theme fitting for a game like this, but near the end, [[spoiler:the narrator tells that she is the only surviving person out of everyone she ever knew, and the final part of the song seems to be narrated days before her death.]]
* MagicMusic: The Song of Dragons is an in-universe example: humanity obsesses over its meaning and origin, and it's become known as a harbinger of doom wherever it is heard. [[spoiler:It's actually a musical key known by all whales that guides people to and unlocks the Okeanides ruins...and subsequently drives the whales within mad to seal it up again.]]
* MagicRealism: The incredibly varied wildlife, all of the sea's animals being tame and friendly to humans, and the Manoa Lai artifacts and legends all seem to be best explained by something other than science.
** The sequel fixes the MisplacedWildlife aspect and the main plot is more AlternateHistory than magic, but the side quests include chasing a magic blue bird that can appear anywhere in the world, fetching items for a tiki idol, and "The Voice of the Night Sky" rewarding you for finding constellation coins scattered all over the world.
* {{Meganekko}}: Kat and Hayako again.
* MisplacedWildlife: ''Lots'' in the first game. Averted in ''Blue World'', which has varied, round-the-globe environments to host all those fish.
** ''Blue World'' also makes sure that, in the event that an animal ''does'' show up where it shouldn't, the characters [[LampshadeHanging point it out]] and puzzle over how it might have gotten there. One sidequest actually has you rescuing some saltwater fish who've wandered into a freshwater river and have become very sick as a result, and the first time you go there you find a ''minke whale'' trapped upstream.
** All your dolphin pals except for the tropical ones get misplaced once they follow you home to sunny Nineball Island. Particularly the river dolphin. [[spoiler: The river dolphin that you get by taking along a '''narwhal''' from the ''Arctic.'']]
*** Granted, that last bit [[JustifiedTrope does have an explanation]]. The animals are male and female in their respective stories, you see...
* MonsterCompendium: The Marine Encyclopedia is a variation on this.
* MouthFlaps: Despite there not being any actual voice work in the game. Even [[HeroicMime your character]] MouthFlaps without even having textual dialogue.
* NatureSpirit: It's hinted that some of the legendary animals are more than just animals. Thanatos [[spoiler: and the Ancient Mother]] are the prime examples of this [[spoiler:but the Blue Bird also seems to be more than it appears.]]
** A more blatant example is the Commerson's dolphin that you can befriend. It is heavily implied, if not outright stated, [[TalkingAnimal to speak]], and is found guarding a treasure room in the uppermost part of a sunken temple.
* NotGoodWithPeople: Kat, first variety.
* OminousLatinChanting: "Benedictus", an unlockable song found in the Abyss area.
* OpeningTheSandbox: ''Blue World'' has a few locations which have limitations imposed on you. Once you do what the plot requires you to do there, you are provided gear which allows you to explore them at your leisure.
* OverlyLongGag: Recruiting the last dolphin partner in the sequel. "Present your ''X'' to the lady!"
* PolarBearsAndPenguins: Played straight in the first game as part of the MisplacedWildlife; averted to hell and back in ''Blue World''.
* PopStarComposer: Music/HayleyWestenra of Music/CelticWoman provides the soundtrack to this game and its sequel.
* RandomEncounters: A non-enemy example in the first game, in the form of "zoom-in" spots to look for the smaller creatures like sea slugs; their positions would shuffle around between dives. ''Blue World'' turned these spots into static PreExistingEncounters.
* RealSongThemeTune: "Prayer" by Music/HayleyWestenra.
* RecurringBoss: Thanatos will attack almost every time you enter his territory.
* RibcageRidge: There's a whale skeleton at the bottom of the Abyss. Also counts as {{foreshadowing}}, since it appears to be the same species as [[spoiler:the Ancient Mother]].
* RightBehindMe
--> '''Hayako:''' "What is with Finley always turning up when we're talking about him? Is he watching us?"
* RoaringRapids: There are a few of these where the character has to hold onto their dolphin partner to swim against them. In other cases, you get blown back with a "The current is too strong" message.
* [[FishingForSole Salvaging For Sole]]: There's an awful lot of trash hidden in unexpected parts of the ocean, such as empty juice bottles found near sealed containers of valuable ingots. But then, of course, this can definitely be TruthInTelevision depending on how often a given location gets human traffic.
* ScareChord: Given that the song "Benedictus" plays when you visit the Abyss in the first game, the crescendo of brass/drums/vocals turns into this, especially when the sperm whale or giant squid suddenly dash into view at the same time.
* SceneryGorn: Most of Ship's Rest.
* SceneryPorn: Most of the earlier areas, and some of the later ones (see: the White Room in Great Aqua Cave.)
* ScienceIsBad: Averted. The mysterious and perhaps Godlike [[spoiler:Ancient Mother]] is captured and taken to the Manoa Lai aquarium without anyone raising a ruckus. You can release it later, though.
** Good luck finding each species (over 240) three times to fill in all of the encyclopedia to unlock this option, though! Serious GuideDangIt moments there.
* ScrewTheMoneyIHaveRules: Kat deciding to keep the piece of deep-sea coral found in the Abyss instead of selling it.
** Also Oceana insisting you keep [[spoiler:the plesiosaur]] a secret.
* SealedEvilInACan: The [[spoiler:Magu Tapah]], which you [[spoiler:have effectively released by befriending the orca that was guarding said can, and bringing it away from Ship's Rest.]] [[InferredHolocaust Oops.]]
* SeaMonster: The Ancient Mother. She returns along with a whole slew of Legendary Beasts [[spoiler: including an actual plesiosaurus]] in Blue World.
* SeriesMascot: The bottlenose dolphin. There are also people who claim that the emperor angelfish or bicolor parrotfish are the game's mascots, due to their both being extremely common.
* ShownTheirWork: Some of the game's detractors say it has a little too much information about fish sandwiched in. Fans say that's just part of its appeal. ''Blue World'' tones down the factoids considerably, but there's still a great deal to learn.
** There are a couple of mistakes, though. They're few and far between, but they're there: for example, the false killer whale you befriend in Blue World can apparently find items with its "keen sense of smell". Cetaceans have a highly-developed sense of taste, but they have no sense of smell in the conventional sense, as their nostrils are closed off most of the time.
* SlippySlideyIceWorld: The Arctic and Antarctic levels in the sequel. They're not very slippery, but they are intensely cold; early dives have a strict time limit until Hayako develops a "special insulating wax" that makes things safer.
* SmallTaxonomyPools: Averted, in as much as time, budget, and disc-space would allow.
* SoundtrackDissonance: Each theme was specifically crafted for one area, and can sound rather silly if you choose to play it somewhere else - for example, filling the cheery little Coral Forest with OminousLatinChanting.
* SpellMyNameWithAnS: The North American releases tend to change up character and location names. "Manaurai" became "Manoa Lai", and C's frequently become K's (Oceanides/Okeanides, Catherine/Katherine).
* SpeciesLostAndFound: In Blue World, at least three animals, [[spoiler: the plesiosaurus, the anamalocharis, and the orthocone]] are supposed to have been extinct for millions of years, but they're found alive and well. They're encountered in cutscenes, but can't really be interacted with.
* SpiritualSuccessor: To the ''Everblue'' games.
* TheStinger: Inverted - instead of extra content during the credits, you can find the credits as an EasterEgg.
* StockSoundEffects: For the dolphins and whales. There's a pool of sounds each for small dolphins, big dolphins, whales, and belugas.
* TheStoic: The player character's defining trait, thus explaining his/her HeroicMime tendencies.
* SuperNotDrowningSkills: There actually ''is'' an air meter, but it expires too slowly to really matter.
** In the sequel, however, the air gauge is more realistically timed, but can still be lengthened by improving Diving Skill and buying regulators and support tanks (the tanks that say "support" in the name, preceded by a capacity; all the others are just cosmetic and only otherwise good for getting the title for having all the tanks).
* SuperPersistentPredator: Averted in the second game; sharks, caimans, and piranha will attack you, but will not chase you for too long before they give up.
** [[spoiler:Thanatos]] plays it straight, but it's implied that he might be more than what he appears.
* SurpriseCreepy: Don't let the lack of combat and mostly serene atmosphere fool you, these games have some awfully scary parts.
* TailSlap: Make no mistake, sharks act very threatening towards you and will rush with teeth bared to approach. But their actual attacks only consist of this.
* TailorMadePrison: Ship's Rest turns out to be this for [[spoiler:the Magu Tapah]].
* TakeYourTime: An overriding theme of the series as part of its laid-back, tranquil atmosphere.
* TalkingAnimal: ''Blue World'' has two possible examples, both during side-quests.
** The first is the blue bird, [[MaybeMagicMaybeMundane though whether this is an illusion, telepathy, real speech or something else is never explained]].
** The second would be during the dolphin-gaining sidequest. The Commerson's dolphin seems to be able to speak. Furthermore, any companions back on the boat can hear him/her over the radio. Once the dolphin becomes your partner, this detail is never mentioned again.
* TempleOfDoom: Mo'ia Atoll is an actual temple, though the worst booby-trap there is a jet of water which impedes your progress. ''Blue World'' has more dangerous examples.
** Valka Castle has [[TheSpiny lionfish]] and a trick door that locks you in.
** The Spirit Falls ruins has [[NeverSmileAtACrocodile caimans]], switch-pulling puzzles, and a [[CaveBehindTheFalls convenient location]].
** [[TheVeryDefinitelyFinalDungeon The Cavern of the Gods]] has water-current traps, dangerous fish that can deplete your oxygen quickly, and [[spoiler:the FinalBoss, the Okeanos Guardian]].
* ThemeNaming: Three characters in ''Blue World'' opt to go by their initials. Salvage master Gaston Gray goes by "GG", salvage client Franklin Fischer is "FF", and there's the mysterious, amnesiac acquaintance of Nancy's who goes by "ML" [[spoiler:who could well be Jean-Eric's son Matthias.]]
* ThreateningShark: [[spoiler:Magu Tapah, [[NamesToRunAwayFromReallyFast Thanatos]], and the [[FinalBoss Okeanos Guardian]]]] say hi. With their huge, tooth-lined, bloodied mouths.
** Besides the legendary sharks, there's also at least five other species of dangerous sharks: Greenland sharks in the Arctic, a tiger shark at Deep Hole at night, a bluntnose sixgill shark in the Abyss, goblin sharks in the Cavern of the Gods, and good ol' great whites all over the Ciceros Strait. None of the sharks actually bite; instead they use a TailSlap attack.
** Averted with many of the other sharks, though. Whale sharks and basking sharks are [[GentleGiant huge but harmless]], and a number of smaller species (hammerheads, for example) are also safe to swim near. The lack of damage in the first game meant even potentially nasty sharks never pose a real threat.
* TimedMission: Technically you can only spend ''x'' number of minutes underwater at a time due to your oxygen tank depleting, but you receive a straighter example [[spoiler:at ''Blue World'''s finale as the whales cause the ruins to collapse.]]
* TitleDrop: Kat does one at the end of the original:
--> "And we can keep trying to protect this amazing, endless ocean of ours."

** In the sequel, the scene where Matthias' letter is read drops both the series title and this installment's NA subtitle. Also, the series title is part of the title for completing that same chapter, the final one in the main story.
* TurtleIsland: After [[spoiler: you rescue the dog, you can find him barking at an island during the day, but the island suddenly disappears. When you go diving near the area, you will eventually find a Legendary Creature: A giant Leatherback Turtle whose shell is easily mistaken for a small island.]]
* UndergroundLevel: Great Aqua Cave, and some parts of the Abyss. [[ExactlyWhatItSaysOnTheTin Deep Hole and the Zahhab Depths]] in ''Blue World''.
* UnderTheSea: Do we really need to explain this one?
* UnderwaterRuins: The Mo'ia Atoll (Marige Atoll in the UK release) area; Triton Village, Valka Castle and the Cavern of the Gods in ''Blue World''.
* {{UST}}: Some hints of it between the player character and Kat, descending into LesYay if you chose a female avatar.
* ViolationOfCommonSense: In the first game, you can pet [[TheSpiny venomous lionfish]] with no ill effects.
** [[ZigZaggingTrope Zig-zagged]] in the sequel; merely brushing up against a lionfish results in the player losing bars from their oxygen gauge. But a whole new series of problems opens up from the wider range of locations, such as [[ExposedToTheElements wearing only swim trunks/a bikini in to the polar regions with no ill effects]], or having a teenager dive to professional-level depths.
** In the aquarium, you can display predator and prey, natural enemies, or freshwater fish and saltwater fish in the same tank at the same time.
** The giant great white shark Thanatos is immune to the pulsar, but you can get his information by allowing him to attack you, after which there's a brief moment when you can focus on him. Good thing sharks don't actually ''bite'' in these games!
* VoiceWithAnInternetConnection: Kat and Jean-Eric.
* WideOpenSandbox
* WhereItAllBegan: The Great Aqua Cave is one of the first places you go in the first game, but you return to it later on and enter the [[spoiler: White Room]].
* WhereTheHellIsSpringfield: The Manoa Lai region is vaguely placed in the South Pacific Ocean, which isn't exactly known for being small. ''Blue World'' averted this with the help of an in-game globe.
* WhyDidItHaveToBeSnakes: Ironically, Kat is severely aquaphobic. [[spoiler:Her father Patrick]] died while on a dive when he got tangled up in kelp and eventually drowned. Seems fairly reasonable that she might have an aversion to diving after that.
* WidgetSeries: Not many gamers knew how to react to a franchise which, compared to other games, has no ultimate goal.
* TheWorldIsJustAwesome: Any time you discover a new major landmark, you're given a cinematic pan-around to showcase it from the best angles, after which you can explore them at your leisure.
* WorkplaceAcquiredAbilities: Oceana illuminates all nearby zoom-in spots and can offer tours of landmarks; Gaston notifies you of nearby salvagables and [[ItemCaddy holds onto five extra items]]; Hayako provides a radar of nearby species and allows for reviewing of special fauna behaviors (read: {{cutscene}}s); and the helper dolphins swim you around faster and can locate specific types of salvagables.
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