[[quoteright:250:[[TheVenusProject http://static.tvtropes.org/pmwiki/pub/images/undersea.jpg]]]]
[[caption-width-right:250:Think of it as your regular secret base. Except instead of birds, you have [[ThreateningShark sharks]].]]

->''"If you're looking for me,\\
You'd better check under the sea,\\
'Cause that is where you'll find me\\
Underneath the Sealab\\
Underneath the water\\
Sealab...\\
[[DepartmentOfRedundancyDepartment At the bottom of the sea.]]"''
-->-- '''{{WesternAnimation/Sealab 2021}}'''

Characters have their base of operations underwater. Somewhat more common with villains. Good for keeping out unwanted visitors. After all, it takes more effort to break in if you have to be looking out for giant squids at the same time.

Compare ElaborateUndergroundBase, IslandBase, SpaceBase. See also UnderwaterCity.

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!!Examples:

[[foldercontrol]]

[[folder: Anime and Manga ]]

* ''{{Daimos}}'': [[WingedHumanoid The Brahmins']] HomeBase on Earth was an underwater base served like their headquarters to launch attacks from.
* ''{{GaoGaiGar}}'': The Gutsy Galaxy Guard's headquarters is an underwater "Harbor Reef Base" located [[spoiler:underneath the Japan Aeronautics headquarters.]] Later, [[spoiler:after the 31 Primevals trash both the Aeronautics headquarters and the base with their attacks]], they relocate to an orbital space station base.
* ''Anime/MazingerZ'': TheDragon Baron Ashura was commander of Dr. Hell's sea and submarine fortresses and had two underwater bases: Salude and Bood.
** ''Anime/GreatMazinger'': Marquis Janus HomeBase was an IslandBase could submerge.
* ''Anime/ScienceNinjaTeamGatchaman'' has had a few, and thus by extension, so did ''Anime/EagleRiders'' and ''Anime/BattleOfThePlanets''.
** The most noteworthy is Crescent Coral Base (Center Neptune in [[Anime/BattleOfThePlanets BotP]]) which had thrusters on the bottom allowing it to physically move and change locations if discovered and projected a fake coral reef above on the water surface to fool people.
** ''Gatchaman II'' had G-Town, a huge mobile base (more like a city) at the very bottom of the ocean.

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[[folder: Film ]]

* The movie ''Captain Nemo and the Underwater City'' puts the city of "Templemere" under a dome at the bottom of the ocean, where the submarine ''[[Literature/TwentyThousandLeaguesUnderTheSea Nautilus]]'' has its berth. And this is supposedly done during a time when the best technology is Steam powered.
* The drilling rig in ''Film/TheAbyss''.
* Stromberg's home in ''Film/TheSpyWhoLovedMe''.
* ''AustinPowers'': "Welcome to my submarine lair! [[DoubleEntendre It's long, hard and full of seamen]]."
* ''Film/GIJoeTheRiseOfCobra'' features one of these as the villains' main base.

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[[folder: Literature ]]

* The research station from ''{{Sphere}}''.
* ''Literature/ASeriesOfUnfortunateEvents'' alludes to the AncientConspiracy owning one.
** Also, [[spoiler:in the Penultimate Peril, Hotel Denouement is actually a library under the water that reflects the hotel. Everything on the hotel is written backwards so that it's correct in the reflection.]]
* Beebe Station from the ''Literature/RiftersTrilogy''.

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[[folder: Live Action TV ]]

* The Rangers' base in ''Series/PowerRangersLightspeedRescue''. Deliberately chosen because water is the demons' WeaksauceWeakness; otherwise, they would have destroyed the base as early as episode 2.
** Series/RescueSentaiGoGoFive had Bay Area 55 (the mecha hangar) protected by magical symbols, providing an effective demon deterrent.
** Series/ChoujuuSentaiLiveman and Series/BattleFeverJ also had underwater bases.
* The ''Series/DoctorWho'' story "[[Recap/DoctorWhoS21E1WarriorsoftheDeep Warriors of the Deep]]" was set in an underwater base, from which nuclear weapons were controlled.
* The ''UFO'' episode "Reflections in the Water" had an underwater alien base.
* The Looking Glass station on ''Series/{{Lost}}'', used by the Others to block all communications coming to the island.
* Series/LostInOz had a heroic version with Bellaridere's underwater palace.

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[[folder: Tabletop Games ]]

* Several new underwater territories have been added to the [[TwentyMinutesIntoTheFuture futuristic]] ''Risk 2210 A.D.'' board game, compared to its original, much better-known, incarnation.
* ''TabletopGame/TranshumanSpace'' features a wide range of established sub-aquatic operations; the most exotic are deep in the ice-covered oceans of Europa, a moon of Jupiter, where a miniature war is being fought for the future of the moon.

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[[folder: Video Games ]]

* The Pasadena Ocean Lab in ''VideoGame/DeusEx'' was just an advanced research facility for the BigBad, and devoid of life[[labelnote:*]]''human'' life, anyway[[/labelnote]], but information there is vital to his plans, and TheDragon makes an appearance.
* The final location of ''VideoGame/WithinADeepForest'', and the setting of the ''VideoGame/KnyttStories'' level ''An Underwater Adventure'', which is an alternate version of ''Within a Deep Forest'''s story.
* There's an abandoned underwater base in ''VideoGame/{{MOTHER|1}}'', which was originally used by [[spoiler:Ninten's great-grandfather]].
* The FinalBoss battle of [[VideoGame/GaiaOnline zOMG]] Chapter One takes place in [[spoiler:Labtech X's]] Underwater Base.
* ''VideoGame/FinalFantasyV'' had the Catapult, an underground/underwater base of LostTechnology. Among other things, it features an airship docking bay, a teleporter and a ship-sized elevator to the sea surface. And the icing on the cake? It's ''[[PlayerHeadquarters yours]]'' now.
* Since ''{{X-COM}} 2'' is basically ''{{X-COM}} 1'' [-UNDERWATER!-], these make up the bases of your organization.
** The alien bases, including [[TheVeryDefinitelyFinalDungeon T'leth]], also apply.
* [[Franchise/SonicTheHedgehog Eggman]] has a few of these.
** Examples include [[VideoGame/SonicTripleTrouble Tidal Plant]], [[VideoGame/SonicAdvanceSeries Ocean Base]] (which has surprisingly little in the way of underwater segments), and [[VideoGame/SonicTheHedgehog2006 Aquatic Base]] (SuperDrowningSkills here).
* The Ocean Palace of Zeal in ''VideoGame/ChronoTrigger'' [[spoiler:at least before it turns into the Black Omen]].
* ''KnightsOfTheOldRepublic'' has one owned by the good guys on Manaan. "Owned" being in the past tense.
* Constructing underwater structures is a popular activity in {{Minecraft}}.
* The deep-sea installation NORAD VI in ''TheJourneymanProject''.
* ''VideoGame/Rockman4MinusInfinity'' had the second half of Dive Man's level. Mega Man finds it by using Rush Marine to dive down to the point where the background is black and heads right.
* ''VideoGame/PokemonRubyAndSapphire'' the undersea base of the villainous team. Which team it is depends on what you're playing. In Ruby, it's Magma, in Sapphire and Emerald, it's Aqua (while Magma's base is instead hidden inside [[VolcanoLair Mt. Chimney]]).
* In the ''Videogame/PokemonPeaceSquad'' games, many Team Aqua bases are this. The exceptions are Aqua Submarine (a [[CoolBoat submarine]]), Aqua Island (an [[IslandBase artificial island]]), and Aqua Galleon (a [[GangplankGalleon high-tech pirate ship]]).
* The Swedish game ''Djuphavsjakten'' ("The deep sea hunt") features this. The exact details are a spoiler: [[spoiler: it features this trope ''twice'', as it turns out -- once you capture the villain's first underwater base of operations, it turns out he has a larger underwater base deeper into the ocean, leaving the good guys to build up the captured base for their own underwater operations]].
* This is the setting for Sega Saturn horror game ''VideoGame/DeepFear'', and used as the justification for the oxygen-counter mechanics.
* Rapture of ''Franchise/BioShock'' of course is an underwater city. More utilitarian areas of it fits this trope.
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[[folder: Web Comics ]]

* Madblood's lair (a later one) in ''Webcomic/{{Narbonic}}''.

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[[folder: Web Original ]]

* The Floridian superheroes known as [[GlobalGuardiansPBEMUniverse the Caribbean Crew]] has a hidden base is sunken off the coast of Key West. From the outside, it mostly looks like a coral reef.
* [[http://www.villainsource.com/ Villain Source]] (Your Online Source For Everything Evil) naturally has one of these for sale. However you have to provide your own aquatic construction personnel. And avoid flooding the place from the [[BigRedButton obvious]] and [[NoOshaCompliance accessible]] control panels.
* ''WebVideo/CoyleCommand'' has Posiedon's vault.

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[[folder: Western Animation ]]

* The Decepticons' ship in the first two series of ''WesternAnimation/TheTransformers''; likewise, Devil Z's base in ''TransformersSuperGodMasterforce''.
* The bioborgs' base in ''WesternAnimation/SkysurferStrikeForce''.
* MAD in ''WesternAnimation/InspectorGadget'' used a few of these.
* So did Dr. Drakken of ''WesternAnimation/KimPossible''.
* ''WesternAnimation/{{Sealab 2020}}'', and by extension, ''{{Sealab 2021}}''.
** Not to mention that ''other'' Sealab featured in ''WesternAnimation/{{Centurions}}'' .
* Lake Laogai in ''WesternAnimation/AvatarTheLastAirbender''.
* In the Pixar movie ''WesternAnimation/TheIncredibles'', the entrance to Syndrome's magnificent ElaborateUndergroundBase is under the sea, built for submersible aircraft to use.
* The Legion of Doom had their headquarters beneath a swamp in the Saturday-morning cartoon series ''Challenge of the Superfriends''.
* Brother Blood designs one on ''WesternAnimation/TeenTitans'' after Cyborg destroyed his first headquarters. Cyborg destroys this one, too.
* Sandy's Treedome from ''WesternAnimation/SpongeBobSquarePants''.
* The Octopod in ''WesternAnimation/TheOctonauts''.
* A villain in ''WesternAnimation/{{Archer}}'' has one that bears [[ShoutOut more than a passing resemblance]] to {{Sealab|2020}}. His StartOfDarkness came from [[CabinFever spending too much time on his own down there.]]

[[/folder]]

[[folder: Other ]]

* Sea Base Alpha in the EPCOT attraction The Living Seas, before the Nemo makeover.

[[/folder]]

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