[[quoteright:300:[[VideoGame/SuperMarioGalaxy http://static.tvtropes.org/pmwiki/pub/images/mario_airmeter.jpg]]]]

Somewhere in between SuperDrowningSkills and SuperNotDrowningSkills lies the '''Oxygen Meter''', which indicates the PlayerCharacter's capacity to hold their breath. If the Oxygen Meter depletes, one of two things will happen: instant death by asphyxiation, or the player character's actual [[LifeMeter health]] will begin to drain.

In [[DownTheDrain water levels]], there will often be designated stops that allow for the oxygen meter to be refilled, such as ceiling vents that allow you to resurface and breathe or [[OxygenatedUnderwaterBubbles bubbles]] that pop up in certain places to automatically refill the meter.

Frustratingly, your oxygen meter is sometimes invisible yet still just as real and waiting to bite you; this is most likely to happen in a first person shooter. This is probably just because the interface is already full and they don't want to waste space on something not even used in most levels... and surprisingly, not all games decided to only make it visible when in use.

It's worth noting that [[TheManyDeathsOfYou dying from lack of oxygen]] is often [[NightmareFuel played unnervingly straight]] even in games where deaths are otherwise cartoonish or even PlayedForLaughs.

An occasional alternative to the Oxygen Meter is to allow only for a finite amount of time underwater before the player character automatically floats back to the surface unharmed--however, this also places a restriction on level design, to avoid the player getting stuck should their "swim timer" run out in the middle of, say, an underwater tunnel or cavern with no air on the surface.

A third way, of course, is to just prohibit underwater travel entirely--either by limiting swimming mechanics to the water's surface (such as in ''VideoGame/{{Bully}}''), using SuperDrowningSkills, or by simply not allowing the player to interact with deep water in the first place using [[InvisibleWall Invisible Walls]]. (Sure, you can still splash around in puddles and knee-high streams, but to go jump in a ''lake''? Are you crazy?)

Games that include a SprintMeter will often replace it with the Oxygen Meter underwater (or use the same meter for both purposes), since actions that use the Sprint Meter are typically unavailable while swimming.

Characters with SuperNotDrowningSkills, by definition, rarely have need of an Oxygen Meter.



* ''VideoGame/GrandTheftAutoSanAndreas''. This was a departure from the rest of the series, as previous games gave the player SuperDrowningSkills.
** The game after this, ''VideoGame/GrandTheftAutoIV'', kept the ability to swim but restricts it to the surface, so there's no meter.
** ''VideoGame/GrandTheftAutoViceCityStories'' also restricted it to the surface, but added a stamina meter which works exactly as an Oxygen Meter; when it runs out, you're screwed.
** And then along came ''VideoGame/GrandTheftAutoV'' which vastly expanded the underwater world, reintroduced the oxygen meter, and added scuba-diving and controllable submarines which allows the player to explore for longer.
* ''VideoGame/AmericanMcGeesAlice'' has this meter for underwater levels where you don't have a shell. Annoying in that the meter is not visible, so you must gauge by bubbles when you're almost out of air. Doubly annoying in that once your health begins to decline, you are given absolutely ''no time'' to find an air source to stop yourself from dying.
* In ''VideoGame/ShadowOfTheColossus'', your stamina meter doubled as an oxygen meter. If it ran out, you would simply let go of whatever you were holding and return to the surface. Because the two are the same, it makes it rather odd when the main character is panting and gasping while completely submerged in the water.
* The 3D ''Franchise/TheLegendOfZelda'' games use both varieties:
** In ''VideoGame/TheLegendOfZeldaOcarinaOfTime'' and ''VideoGame/TheLegendOfZeldaMajorasMask'', diving while swimming normally only lasts for a few seconds before Link resurfaces. Equipping the Iron Boots in the former game lets Link stay underwater longer, in which case a timer based on how much health you have appears (unless you also equip the Zora Tunic, which lets you breathe underwater). These two items are important in the Water Temple. ''Majora's Mask'' merely requires Link wearing the Zora Mask to eliminate the swimming restrictions.
** ''VideoGame/TheLegendOfZeldaTheWindWaker'' does not have any underwater breathing, but does have a stamina bar to prevent you from swimming from island to island (which can only be done by sailing your boat).
** ''VideoGame/TheLegendOfZeldaTwilightPrincess'' has a blue bar that appears whenever Link is sunken underwater with the Iron Boots. Once again, wearing the Zora Armor will allow him to swim for as long as he wants.
** ''VideoGame/TheLegendOfZeldaSkywardSword'' has an oxygen meter as well, which is barely of note until you get the Water Dragon's Scale (Link automatically floats upward when he's not focused on swimming). It resembles the SprintMeter in blue instead of green. Staying underwater depletes it, using your spinning attack depletes it faster, and whatever you do, don't inhale the purple-colored bubbles (they're toxic). Running out of oxygen will quickly drain [[LifeMeter hearts]] until Link surfaces or drowns. There is a potion that slows the rate Link consumes oxygen, as well as a potion medal that prolongs the effects of potions (including the air potion); using the two at the same time makes the difficult Tadtone quest (which takes place underwater) much more manageable.
* ''VideoGame/MonkeyIsland'':
** While oxygen seems to be unlimited in the games, if Guybrush Threepwood stands around underwater for a really long time, he will die. This is really more of a gag death, as it's literally the only way to die in the games. This is, of course, in reference to Guybrush's special talent to hold his breath for ten minutes (a fact he'll repeat to anybody willing to listen). You literally have 10 minutes to solve this puzzle/get out of the water, which is intentionally much longer than most people will need.
** In ''Tales of Monkey Island'', Guybrush can intentionally go underwater, and if you spend a little less than ten minutes of gameplay underwater, Guybrush will remember his limit and go back to dry land. Thankfully, there's only really one or two areas where you need to be underwater, they're incredibly straightforward to navigate, and like it's been said before, ten minutes is a generous amount of time.
* The remake of ''VideoGame/NinjaGaiden'' has one of this, but it ceases to be an issue once Ryu acquires an oxygen tank and draws on it from his HyperspaceArsenal.
* In ''VideoGame/BanjoKazooie'', when the Oxygen Meter runs out, you immediately drown. [[ThatOneLevel Rusty Bucket Bay]] has oily water that not only drains the meter twice as fast when submerged, but drains it at the regular speed ''when on the surface''. This is rectified slightly in ''Banjo-Tooie'', where once the Oxygen Meter goes, your health starts to go down really quickly instead (this is also the case for areas where oxygen is depleted due to toxic airs or very naughty smells).
* ''VideoGame/EccoTheDolphin''. {{Justified|Trope}} of course, since the whole game was set underwater and dolphins can hold their breath for quite a while. When the oxygen meter runs out, health begins to drain.
* In addition to being a certified death incarnate, Rico Rodriguez in ''[[VideoGame/JustCause Just Cause 2]]'' can swim underwater for a ridiculously long (for a video game, at least) amount of time. His oxygen is counted by a small circle that counts down from 99 by two every 2 seconds. This means that Rico can stay underwater for approximately one minute and 50 seconds, which is around what a fit human can accomplish in real life. Not quite SuperNotDrowningSkills, but quite impressive compared to other games.
* ''Franchise/TombRaider'' uses a couple of variations on this:
** While most of the games use a standard oxygen meter, ''VideoGame/TombRaiderChronicles'' used a special diving suit on one level that had confusing ([[GuideDangIt since they never told you]]) additional mechanics: the suit had near infinite air, but as you bumped into walls and rocks, Lara audibly becomes stressed and begins breathing heavily, at which point you begin to lose oxygen quickly, meaning you had to avoid hitting things.
** ''VideoGame/TombRaiderIII'' also has an underwater propulsion vehicle that makes you move faster, but it's less useful than just swimming as it decreases your general mobility and must be got off of to use switches and other items. Water in arctic levels also had a hypothermia bar that went down faster than the oxygen bar, but functioned much the same way.
** In ''VideoGame/TombRaiderLegend'' and ''VideoGame/TombRaiderAnniversary'', oddly, Lara is much slower underwater and has a much shorter air meter.
** ''Videogame/TombRaiderUnderworld'' changes things up again, with Lara going back to being almost as fast as in the original games, and having such a long oxygen bar it borders on SuperNotDrowningSkills (that is in the rare instances where she swims without scuba gear, where it is that trope).
** Decrease in health also functions differently depending on the game. Prior to ''VideoGame/TombRaiderLegend'', health usually decreases at a fixed steady rate. During and after ''Legend'', the decrease in health rate is usually a slash of a quarter of the health bar every two seconds, or an eighth, depending on the difficulty level setting.
* ''VideoGame/ConkersBadFurDay'' has one of these once you're able to swim underwater (namely after consuming some pills in the Poo Cabin). When you're underwater, Conker's face and a stream of bubbles represents your air. As your air runs down, the stream of bubbles grows shorter, and Conker's expression becomes increasingly desperate. And his face starts turning blue as well. When his head droops, your chocolate bar (i.e., your health) starts falling apart rapidly. All six pieces go in about five seconds, so unless you're near the surface anyhow, you run out of air and die.
* In ''VideoGame/AnUntitledStory'', you even get upgrades that extend your oxygen meter.
* ''VideoGame/EndlessOcean'' essentially averts; it *does* have an oxygen meter for your air tanks, but it's a rather long one and most tasks get completed without running out of air ever being a factor. When it does run out, you get warped back to the boat. The sequel does tweak things a bit; dangerous fish attacking you knock your air out faster. Certain equipment upgrades up your air supply in both games.
* An example without water: ''LEGO Franchise/RockRaiders'' had a meter measuring the remaining oxygen in the various caverns. Some levels had infinite oxygen, but in others it would be gradually consumed by your Rock Raiders. In those levels, building at least one Support Station is critical[[note]]also the victory condition in one level[[/note]], as it provides enough oxygen for up to nine miners to work worry-free.
* ''VideoGame/DeepFear'' counts down the amount of air left in any given room. Firing your weapon makes it go down slightly faster. When it reaches 0, you pull out a backup air supply that carries over from room to room (and is mandatory in some rooms which are flooded with water or filled with poisonous gas). When that runs out, you asphyxiate. This is intended to add a layer of tension to the game; however, various panels in the levels can refill the air supply in both the rooms and your backup air, seemingly infinitely, and special air grenades exist to fill any given room up with air as well, which are plentiful in supply.
* ''VideoGame/{{Dishonored}}'' has one of these for you. The [=NPCs=], however, [[SuperDrowningSkills aren't so lucky, as they die the second a single polygon touches water]]. This is particularly frustrating in a PacifistRun, as the game gives no indication of this, other than when Sokolov instantly dies if he is dropped in water (with the player having to drag his unconscious body back to Samuel, so this is basically GameOver).
* ''VideoGame/ShadowMan'' has a rather short one for Mike when he's in Liveside, and running out means instant death. As Shadowman, he becomes an immortal Zombi and has no need for air. Fittingly, underwater sections in Deadside tend to be much longer than they are in Liveside.

* ''VideoGame/SuperSmashBros Brawl'' has an invisible one just for swimming. Some characters (e.g. Squirtle) can swim longer than others (e.g. Charizard), but anyone will sink eventually. In the Subspace Emissary, some stickers can increase the length, but there really isn't any need for it.

[[folder:First Person Shooter]]
%%* Many ''Franchise/JamesBond'' first person shooters.
* In the ''VideoGame/HalfLife'' series, your [[PoweredArmor hazardous environment suit]] provides you oxygen for a limited time. Oddly, the same meter that powers your sprint ability and flashlight is used for this in the second game. Once the suit runs out, Gordon has to start holding his breath. Once ''that'' runs out, your health starts dropping, but you can refill the health that you lost from drowning by coming up for air.
** Health lost to drowning being replenished by coming up and a line from the first game's tutorial sequence suggests that when you go underwater in the first game or the suit's auxiliary power runs out in the second, Gordon is merely holding his breath; when health starts dropping, it's a sign that he used up the air in his lungs and [[FridgeBrilliance what we see as his health actually represents his blood oxygen levels in this case]]. Just like in real life, staying underwater kills him because he holds his breath for so long he passes out from lack of oxygen - [[CaptainObvious which is indirectly fatal when it happens underwater]], especially if no one's around to pull a comatose scientist and his who-knows-how-heavy PoweredArmor out of the dip. Still doesn't explain how he [[SuperDrowningSkills runs out of air so quick]]; maybe the suit's weight makes him have to exert more force to move underwater, using up air faster than normal. On the other hand, he IS a [[SquishyWizard mere scientist, not a soldier or hobby swimmer]].
** ''VideoGame/HalfLife2'''s auxiliary power supplying him oxygen can be explained away by his suit using that electricity to electrolyse oxygen from the water as he swims. Once that runs out, it's back to good old lungs.
* In the first ''FarCry'', your SprintMeter doubles as a Oxygen meter. It makes sense, because if you sprint for an extended period of time, ''what'' are you going to have to catch?
* ''VideoGame/FarCry2'' had your standard oxygen meter that, once empty, would begin to drain your life instead. However Far Cry 2 ''also'' allows you to heal for free with the press of a button. This wonderful GoodBadBug led to what the fans call [[https://www.youtube.com/watch?v=enb0zWbYUik DEADLY AFRICANIZED WATER]]: you can swim for an eternity in it, provided to stop every so often to pull the barbed wire out of your flesh that the water inexplicably leaves there. Later games corrected this by merely having you drown when your breath ran out.
* Bungie's ''VideoGame/{{Marathon}}'' series feature an especially heinous, literal Oxygen Meter: Your armored suit's {{HUD}} doesn't indicate how much oxygen remains in your lungs and blood, but in ITS compressed oxygen tanks! Since your suit lacks any way of refilling it with ambient oxygen, you must locate compressed oxygen dispenser panels or tanks of compressed oxygen to refill it. Worse yet, the player character apparently refuses to hold his breath, as if his suit's tank is empty he will [[CriticalExistenceFailure instantly faint from even momentary immersion]].
** It's rare to have trouble with Oxygen underwater (or sewage, or lava), but the back-to-back vacuum levels (three in a row, if you visit a secret level) in ''Marathon Infinity'' have a nasty reputation. The one vacuum level in ''Marathon'' was also infamous.
** Compare this with the ''Franchise/{{Halo}}'' series' Master Chief/playable Elites, who can apparently stand around forever without anything to breathe.
* ''VideoGame/{{Turok}}'' has a fairly unremarkable one, although you'd kind of expect a muscled-up warrior like him to be able to hold his breath a bit longer.
* The ''VideoGame/{{Thief}}'' games have an oxygen meter that looks like a line of bubbles across the bottom of the screen. If you knock someone unconscious and dump him in water, he will die in about the same span of time you would (so don't dump unconscious guards in swimming pools if you're running a no-kill mission).
** Averted in ''VideoGame/ThiefDeadlyShadows'', where Garrett has learnt SuperDrowningSkills.
* ''VideoGame/AlphaPrime'' uses an OxygenMeter on the asteroid's surface, refillable through the use of oxygen dispensers, or simply by walking back into an airlock.
* ''VideoGame/WillRock'' has the traditional meter for the underwater sequences. If it runs out, you can always replenish your health with healing packs and bandages if they're at hand.
* A variation from ''VideoGame/{{Metro 2033}}'': your wristwatch tells you how much time you have left on your gas mask before you need to switch filter canisters. Spend too long in areas with toxic atmosphere and you die. Since there's no HUD, you have to check your wristwatch constantly to see how much time you have before you have to change filters. And just because you're required to wear the gas mask doesn't mean it can't be damaged either, making any surface expedition a tense journey to avoid any serious conflict. You also need to remember to take off the mask as soon as it's safe to breathe, or it might get damaged the next time you get attacked.
* While you don't get a visible oxygen meter in VideoGame/TeamFortress2, stay underwater too long and your character will begin to take damage and make choking noises as the screen tints blue round the edges with each "hit" taken, eventually dying in the same manner as an environmental hazard when their health runs out. As with the ''Half-Life'' and ''Quake'' series above, health lost from drowning is restored by coming up for air, but pauses if you go back underwater. Oddly enough, Medics and Dispensers can heal players faster than drowning can kill them, so they're sort of like oxygen masks or tubes.
* ''[[VideoGame/{{Doom}} Doom 3]]'' has the oxygen meter only visible outdoors. You can even refill it by getting scattered air canisters.
* In ''VideoGame/BorderlandsThePreSequel'', the player can go out onto the open-space surface of the moon where the game takes place. The player's oxygen tanks will slowly deplete, but can be instantly replenished by entering pressurized areas or by collecting oxygen canisters. The only character whose oxygen doesn't slowly deplete is Claptrap due to being a robot.

* ''VideoGame/WorldOfWarcraft'' has two of these. A traditional oxygen bar for underwater, and a fatigue bar to prevent you from swimming out too far.
** The first one can be bypassed by potions or spells. The second one on depleting completely begins draining your health, and can be circumvented by healing yourself to easily swim to the end of the map. The undead Forsaken can also stay underwater for much longer. This used to be significantly more useful until they extended the oxygen bar for all players, so that now everyone usually has plenty of time to fulfill their task.
*** They can't seem to decide on how long the oxygen meter should be, before the ''Burning Crusade'' expansion, and shortly into ''Wrath of the Lich King'', it was one minute long, halfway through wrath, they increased it to roughly five minutes, and as of ''Cataclysm'', it's back down to roughly two minutes.
*** As of ''Mists of Pandaria,'' the Forsaken no longer have a longer oxygen meter than the other races.
* ''VideoGame/DungeonsAndDragonsOnline'' has a breath meter whenever a PC goes underwater. When the bar empties, the character starts taking damage. Unfortunately, surfacing does not heal any damage taken due to drowning.

* ''VideoGameDistortedTravesty 3'' has a blue bar on the left side of the screen that appears whenever your head is below the water. Additionally when it's within five seconds of running out [[https://youtu.be/xTkDI0cUj_4?t=1m28s big green numbers appear]] right above the player's head and start counting down.
* ''VideoGame/{{Holdover}}'' gives Marie a meter that can be upgraded by collecting blue hearts around the facility. You'll need it, too. She spends a lot of time underwater.
* ''VideoGame/HadesVanquish'' has one that is also Mana's health meter (similar to the next example below). So how long she can hold her breath underwater from a dive depends on how much damage she took beforehand. So in some cases, diving underwater at low health can be [[{{Unwinnable}} borderline suicide]] without any items to recover her health or revive her after drowning.
* The first four 3D ''Franchise/SuperMarioBros'' games have one (''[[VideoGame/SuperMario3DLand 3D Land]]'' and ''[[VideoGame/SuperMario3DWorld 3D World]]'' allow the player to swim indefinitely since they play closer to the 2D games). The original ''VideoGame/SuperMario64'' makes the odd decision of using the LifeMeter in lieu of a separate oxygen meter, while still allowing you to catch your breath when surfacing, which basically means that you can refill your health for free by swimming around at the surface of any deep body of water, or continue holding your breath as long as you gather coins (which heal your life meter). ''VideoGame/SuperMarioSunshine'' and both ''[[VideoGame/SuperMarioGalaxy Galaxy]]'' [[VideoGame/SuperMarioGalaxy2 games]] use a separate oxygen meter (though coins still refill it when underwater, and in ''Sunshine'', it basically replaces your health meter while you're underwater).
* The ''VideoGame/TyTheTasmanianTiger'' games use the Mario 64 variant, sharing the properties of being an oxygen meter and an energy meter, with exactly the same consequences.
* The first ''VideoGame/RatchetAndClank'' game. Ratchet then gains an oxygen mask about halfway through the first game -- and unlike [[BagOfSpilling most of his weapons and items]], the mask makes it to every subsequent game, making it a non-issue for the rest of the series.
* ''Franchise/SonicTheHedgehog'':
** Two-dimensional games give the character an invisible oxygen meter, with a countdown from 5 to 1 followed by automatic death when it runs out (the indication of how much time remains is based on a background music that plays gradually faster).
** This is the same case for the first ''VideoGame/SonicAdventure'' game, but in its sequel, two-thirds of the cast dies upon falling into water (save the small patch in the Chao Gardens). This eventually became the case for everyone over the course of the 3D series while the 2D games retained the classic countdown. Such is the case of the underwater Knuckles level "Aquatic Mine", which can be quite dangerous until you find the infinite oxygen item.
** Averted in some levels, where Sonic displays SuperDrowningSkills, dying if he so much as touches the rippling water at the very bottom of the game world (if you're lucky, he may only lose rings, and bounce back onto land). On others, water is a relatively benign substance, merely reducing your running speed and jump height (swimming is out of the question), and in ''some'' cases (where it takes up a significant portion or even all of the level) requiring you to find air to breathe. Worse, there are even some places where the two are mixed; go too deep on, say, the (GameGear, Sonic 1) Jungle zone or the Aquatic boss fight, and you'll instantly pop your clogs.
* ''VideoGame/CaveStory'' has an oxygen meter which appears when the protagonist is underwater, although one might wonder why, since he's a robot. Players trying for the [[MultipleEndings secret ending]] will eventually discover while saving Curly that surface robots are programmed to shut down if their systems get flooded with water, but this leads one to ask how carrying an oxygen tank enables one to survive underwater indefinitely.
* ''VideoGame/TheNewZealandStory'' did this, with the added implication that it may have actually been water in Tiki's lungs -- swimming up to the surface would naturally allow your oxygen level to (slowly) replenish itself, but the process could be accelerated by spitting water. Pretty deadly water it was, too, as it could kill most enemies.
* ''Radical Rex'' plays this entirely straight. Not only do you get a bar, but you have to either surface to refill it, or (ugh) lock lips with a big fat fish that is somehow able to maintain neutral buoyancy despite apparently being full of air. Oh, and if you touch the un-inflated fish (which this type will become upon giving up its payload), you'll lose a big chunk of air. There are also "bubble" powerups good for about half a deep breath. And if you get caught in the anemone's tentacles, the meter drains almost immediately to zero (though whether it's this or some kind of poison in them that kills you is debatable).
* ''[[VideoGame/JungleHunt Jungle King / Jungle Hunt]]'' uses this during the swimming levels.
* All three ''VideoGame/DisneysMagicalQuest'' games have them, but the meter is only visible in the third.
* In ''Videogame/JablessAdventure'', your oxygen counts down from 100. It happens so quickly that you really can't accomplish ''anything'' underwater prior to receiving the SCUBA gear (which allows you to stay underwater indefinitely).
* ''VideoGame/KirbyMassAttack'' is one of the few games in the ''VideoGame/{{Kirby}}'' series which has this meter.[[note]]This could be justified, as this is one of the only games to not feature Kirby in scuba gear when underwater.[[/note]] This meter is shared by all the Kirbys and the more Kirbys the player has, the bigger the meter is.
* The ''VideoGame/{{Rayman}}'' series plays with this a bit. The first game has SuperDrowningSkills, the second has an Oxygen Meter which can be refilled by collecting blue lums, and the third lets you breathe underwater indefinitely.
* ''VideoGame/SpacePanic'' may have been the first game to have an oxygen meter, though it was really no more than a [[TimedMission level timer]] labeled "oxygen."
* ''VideoGame/MagicalDoropie'' gave Doropie an oxygen meter in the underwater base levels. When it got low, it would beep until refilled by jumping into a convenient air pocket.
* ''Videogame/{{Endeavor}}'' has an oxygen bar, which replaces the endurance meter when you're underwater. Getting the Flippers item in game slows down how fast your oxygen depletes.
* ''VideoGame/DonkeyKongCountryTropicalFreeze'' has a meter that applies to all Kongs, both when played as together or separately. Touching air bubbles or items surrounded by air will replenish the meter.
* ''VideoGame/OriAndTheBlindForest'' has an oxygen bar that lasts for roughly 15 seconds before Ori's health begins to drain. Strangely, drowning in this game is the only way to die that doesn't employ CriticalExistenceFailure (Ori clutches at their throat and visibly inhales a lungful of water upon death, rather than exploding into a shower of magic sparks as usual), and can be averted entirely via an upgrade that ditches the meter for SuperNotDrowningSkills.

* Non-underwater example: the ''VideoGame/MrDriller'' series has an Oxygen meter that slowly depletes as you play, with the oxygen loss accelerating once you make it deeper underground. To stay alive, you need to pick up air capsules scattered throughout the mine.
* One type of puzzle in ''The Time Warp of VideoGame/DrBrain'' had you controlling a lungfish in an underwater maze. The lungfish would gradually change colors from bright green to purple as your oxygen ran out. [[OxygenatedUnderwaterBubbles Eating bubbles]] or finding an air pocket replenished it.
* The HiddenObjectGame ''Hidden Expedition: Titanic'' was structured as a series of dives to the wreck of (you guessed it) the Titanic. The timer for each level was a [=SCUBA=] tank, that vented a little extra air with each mis-click. Some of the levels also had a second tank hidden in one scene, and finding it gave you some extra oxygen/time.
* Played with in the indie browser game "Asphyx" where you explore a partially-drowned mine. YOU are the oxygen meter. Yes, YOU are supposed to hold your breath when you are underwater.

* ''Franchise/TheElderScrolls'':
** ''VideoGame/TheElderScrollsIIIMorrowind'' and ''[[VideoGame/TheElderScrollsIVOblivion Oblivion]]'' have "Breath" meters; if the breath meter empties, the player's health begins to drain rapidly. Can be circumvented using a Water Breathing spell or playing as the [[LizardFolk Argonian]] race. ''[[VideoGame/TheElderScrollsVSkyrim Skyrim]]'' keeps the meter, but makes it invisible -- so the only indication that you've been underwater too long is when your health starts draining. ''Skyrim'' also removed the ability to cast spells underwater, so you can't just infinitely cast and re-cast water breathing spells to stay underwater longer. Unless you have a ton of waterbreathing potions or are playing as an Argonian, your oxygen meter ''will'' limit your time underwater. (Just don't think about how you're managing to drink potions underwater.)
** In ''VideoGame/TheElderScrollsIIIMorrowind'', there is a quest which requires you to [[FissionMailed drown yourself]]. Even [[GuideDangIt if you manage to figure out that you are meant to do this]], your character takes a fixed (and minor) amount of damage for each second that they are underwater without air, meaning that it can take a high-level character at full health a ridiculous amount of time to finally drown. You'd also better make sure to take off any health-regenerating items first.
** ''VideoGame/{{Fallout 3}}'' and ''VideoGame/FalloutNewVegas'', which use the same engine, inherit this effect from Oblivion as well. It drains worryingly quickly, followed by massive health loss. Although a character in New Vegas can gain SuperNotDrowningSkills with [[spoiler:the unique rebreather]], again based on the very same effect as Water Breathing in Oblivion.
** An interesting variation on this is that the meter is more and more forgiving as you increase your Endurance attribute.
** Amusingly, some creatures in New Vegas will follow you underwater, despite having their own oxygen meter.
* In ''VideoGame/DeusEx'', your health would also start decreasing when you run out of oxygen and start gulping water. While there are [[InstantExpert skills]], items, and {{Upgrade Artifact}}s to increase the amount of time you can hold your breath, the powerful health regeneration Upgrade Artifacts and instant-use [[HealThyself medkits]] allow one to use HitPoints as an extra Oxygen Meter.
* Swimming underwater in ''VideoGame/{{Gothic}}'' adds an oxygen meter in addition to the player's health and mana meters. When the Nameless Hero runs out of oxygen, the health starts draining instead, until he runs out of health and drowns. Notable because surfacing will make the meter invisible again, but will ''not'' instantly refill it -- the player must stay on the surface for at least a few seconds, or will find on diving again that the meter isn't completely full.
* In ''VideoGame/MegaManBattleNetwork 5'', there is a water dungeon which you have to guide your current Navi through. While they are underwater, they are perfectly fine until they run out of "cyber-air" (really?), at which point their HP starts dropping rapidly until you either hit a cyber-air pocket or exit the water. Oh, [[FakeDifficulty and there's random encounters the whole way, including while you're attempting to fight the currents that push you back and drain your air, and while you're trying to avoid the whirlpools that drain your air.]] There's also three areas of this, each one progressively more frustrating. This is one instance Capcom cut something out of the English release for a good reason -- in the Japanese version, there were four areas. By the DS version, it was back up to four.
* When traveling on the ocean floor to Tane-Tane Island in ''VideoGame/{{Mother 3}}'', the way you refuel your characters' collective oxygen bar is unusual. The amount of time you're able to survive without the aide of these machines is fairly realistic compared to most examples, though -- around 30 seconds to a minute (with battles excluded). You get them [[HoYay kissed by big-lipped mermen]]. And if you run out of oxygen, you don't die -- instead you get washed up on the beach at the beginning and have to start the underwater "dungeon" all over again.
* In ''VideoGame/FinalFantasyVII'', the party has twenty minutes to defeat [[BonusBoss Emerald]] [[UnderwaterBossBattle WEAPON]], unless a party member is carrying the "Underwater" Materia, which replaces the timer with SuperNotDrowningSkills.
* There's an optional underwater dungeon in ''VideoGame/FinalFantasyV'' that gives you a timer. The boss is a PuzzleBoss, just to make things more "fun". It's Gogo the Mimic. How do you win? [[spoiler:Do nothing. He's testing to see if you can be a good mimic -- so mimic him mimicking you doing nothing.]] The faster you catch on, the more time you have to get out.
* ''VideoGame/SuperPaperMario'' uses a meter like this, but not for oxygen -- the one place where Mario needs oxygen, [[ItRunsOnNonsensoleum he can somehow get all he ever needs from a goldfish bowl]]. No, the meter comes into play when shifting into 3D, where it depletes steadily and does damage if it runs out.
* ''VideoGame/MonsterHunter Tri'' and ''3 Ultimate'' use an oxygen meter during underwater combat, though the amount of time the player character can hold their breath for is a bit unrealistic, just not enough so that you're not forced to return to the surface, find oxygen bubbles underwater, or use a miniature oxygen supply bauble. One of the major fights in the game takes place exclusively underwater, so this becomes very important. Eating certain food combinations or using an Air Philter or Mega Air Philter will extend your already-generous oxygen meter, and raising the Oxygen skill to 10 points grants you the [[SuperNotDrowningSkills Endless Oxygen]] skill.

* ''VideoGame/{{Minecraft}}'' gives you small air bubbles underwater. Once used up, you lose health over time, and originally began recoiling from damage, making it VERY hard to surface(this was eventually patched out). Helmets enchanted with the Respiration ability decreases oxygen consumption, including drowning damage.
* ''VideoGame/{{Terraria}}'' has an air meter that appears and depletes gradually when your character enters water (or lava, but if you're swimming around in that you generally have [[ManOnFire other problems]]). It allows you a decent amount of time, and if you're doing a long stint of underwater mining, you can always dig into a wall to create your own air pockets. Certain pieces of equipment like the Diving Helmet or the Breathing Reed make the meter deplete more slowly (the Breathing Reed also allows breathing if the end is still above the surface). The game also provides the Gills Potion, which makes you start drowning in air instead of water, and Neptune's Shell, which turns you into a FishPerson and allows you to swim and breathe. Amusingly, if you attempt to equip a Fish Bowl as a helmet, you start drowning as if you were underwater. Which you kind of are, as far as breathing is concerned.
* ''VideoGame/{{Starbound}}'' gives you an air meter that appears and depletes when you're submerged in liquid (water/tar/poison/lava) or if [[AvertedTrope you're]] [[BatmanCanBreatheInSpace in space]], damaging the player rapidly once it fully empties. Equipping the [[ArtificialGill Survival System]] removes this oxygen meter. Strangely enough, even the [[RidiculouslyHumanRobots Glitch]] and [[FishPeople Hylotl]] races still have this oxygen meter when underwater.

* ''SteelBattalion: Line of Contact'' adds one in the form of your view whitening up when the cockpit hatch is closed and your VT is shut down (either manually by toggle switches, the Rapier's Stun Rod, or the Earthshaker's Gauss emitter). Go without oxygen for too long and the pilot asphyxiates, taking you out of the match even if you have enough sortie points for another VT and deleting your pilot data.
* The ''[[VideoGame/{{X}} X-Universe]]'' gives you a two-hour air supply on your spacesuit, though checking it requires you to open up the spacesuit's info screen. Two hours is usually plenty of time for you to do whatever you need to, although it's possible to run out if you're trying to patch up a capital ship's hull with the suit's [[HealingShiv repair laser]]. Somewhat bizarrely, when your oxygen runs out, you explode.
* ''VideoGame/FisherDiver'' has an oxygen meter that not only goes down when you dive underwater, but also whenever you use weaponry on the fish that swim in the ocean's depths.

[[folder:Stealth-Based Game]]
* In the {{Water Level}}s of ''VideoGame/AssassinsCreedIVBlackFlag'', Edward will slowly run out of air, shown on a meter. He can replenish his air by sticking his head in various pockets of air contained in overturned barrels or underwater caverns, or by simply returning to the diving bell used to reach the sea floor.
* All the ''VideoGame/MetalGearSolid'' games feature an oxygen meter, which determines how long you can [[MemeticMutation MANAGE TO AVOID DROWNING]] underwater, survive poisonous gas, or resist being strangled.
** The first game, even though there is ''no'' reason to backtrack all the way to the heliport after acquiring the gas mask, took the time to distinguish between water and gas just in case [[TheDevTeamThinksOfEverything the player decided to take the gas mask all the way back to that briefly flooded air vent to see what happens if you wear it.]]
** Both Vamp and Liquid Ocelot, as bosses, also feature oxygen meters. The former has to resurface from the waste water when his meter empties (which you can speed up by shooting him or literally knocking the wind out of him by tossing in a grenade), while Ocelot's is purely cosmetic and only pops up when you're strangling him.

[[folder:Third Person Shooter]]
* ''VideoGame/DukeNukem Time To Kill'' deviated from the [[VideoGame/DukeNukem3D first-person variant]] by actually providing the player with a LCD heads-up oxygen meter. There was the added caveat, however, of no scuba gear to be found.
* In ''Franchise/DeadSpace'', this becomes visible once you enter a vacuum. As it depletes, Isaac begins to choke and gasp, which is just wonderful for your concentration. Thankfully, your time limit can be extended with upgrades to your RIG and restored with air canisters.
* ''VideoGame/MassEffect1'' features a variant; it lacks an actual ''oxygen'' meter, but many levels have environmental hazards in the form of extreme heat, cold, or gravitational pressure. The player is safe inside their vehicle, the Mako, but if they leave the vehicle, a meter will appear and slowly deplete. If it empties, the player dies, but the meter instantly fills back up if the player enters the Mako or a pressurized environment such as a building. Equipping certain types of armor that were noted as having been designed for use in hostile environments would slow or possibly even stop the meter from draining.