"It seemed a sure bet that by the early '70s we'd be flipping a coin as to whether we'd be spending our holidays on the Moon or at the Poseidon Hilton on the bottom of the Caribbean."Not just Underwater Ruins or an Underwater Base, but an entire city of people living and "breathing" underwater. It's usually created with futuristic technology or powerful magic, and a popular depiction is to have a fully surviving Atlantis with domes and/or water breathing Fish People or Apparently Human Merfolk. Usually though it's a modern attempt at colonizing the ocean floor, or a villain's secret lair. As might be expected, living in such a precarious location makes these cities inordinately prone to having something go Horribly Wrong. Be it sabotage causing the dome to break, an undersea volcano activating, or other disasters. See also City on the Water for cities atop the water instead of underneath. Compare Underground City.
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Anime & Manga
- Daphne in the Brilliant Blue: The main cities of the aquatic New Eden were originally Underwater Cities created to escape the apocalypse. Heroine Maia is the last survivor of one of the cities which was destroyed before it could surface.
- The Fishman Island in One Piece is actually a big mass of land floating in a 2-layer resin bubble, underwater. The light source come from the mystical Sunlight Tree Eve, which transfers sunlight from the surface to the ocean deep.
- Nagi-Asu: A Lull in the Sea has Shioshishio, a small town of Apparently Human Merfolk near a Japanese town on the coast. There's substantial friction between the neighbours over things like fishing rights.
- In Scion, Ethan discovers an underwater city built by an aquatic sub-species of the Lesser Races who were able to escape their lives of slavery.
- Both Marvel Comics and DC Comics have versions of Atlantis, although in both cases Atlantis is a big place with multiple cities.
- There was an arc in Aquaman where half of San Diego slid into the sea following a massive earthquake... and those who survived it instantly adapted to underwater conditions.
- The Elements Of Friendship gives us Lyonesse, the capital of Aquastria.
- City Beneath The Sea (1971)
- The City Under The Sea (1965), AKA War Gods of the Deep
- The Underwater City (1962)
- Otoh Gunga, home of the Gungans from the Star Wars prequels.
- The Abyss, in which the NTIs have a very large habitat on the ocean floor. (Whether it's a city or an enormous starship is never really made clear.)
- The Shadow Over Innsmouth by H.P. Lovecraft has Y'ha-nthlei, of the "titanic sunken porticos" and "labyrinths of weedy cyclopean walls." Located off the coast of Massachusetts and home to the Cthulhu-worshipping Deep Ones.
- And don't forget Cthulhu's own sunken city of R'lyeh.
- Isaac Asimov's Lucky Starr and the Oceans of Venus.
- Michael Reaves and Steve Perry's novel Dome, which is set in a futuristic underwater lab complex.
- Underwater colonies are a significant part of the backstory of "The Eve of RUMOKO" by Roger Zelazny.
- A city of cray (lobster-centaurs) is featured in China Miéville's The Scar.
- In Attack from Atlantis by Lester del Rey, a submarine crew discover an ancient underwater civilization.
- The great city of hi'Leyi'a on the planet Pacifica, in the Star Trek Novel Verse. First mentioned in Star Trek: Titan, it finally appeared in Losing the Peace.
- Handled as realistically as possible in "Ocean on Top" by Hal Clement. A colony of humans is established on the ocean floor, using geothermal power to provide light and a specially-made oxygen-carrying dive fluid in place of air. But since the humans are less dense than water, the humans have to wear weights if they want to stay on the bottom or even have neutral buoyancy. They sleep tied to the ceilings of their buildings.
- Somewhereinitaly in Almost Night. There was also a city called Somewherenotinitaly, but it was destroyed by the Deep Ones.
- The "Undersea" trilogy by Frederik Pohl and Jack Williamson (Undersea Quest, Undersea Fleet & Undersea City) have underwater domed cities protected by Applied Phlebotinum ("Edenite" forcefields). Think of Robert A. Heinlein's Space Cadet done underwater.
- Animorphs has an odd book where the heroes, plus Visser Three, get trapped in a city in an underwater cave. The inhabitants are amphibious mutants whose race is dying, which means that they harvest any humans who sink for DNA.
- They also visit the City of Worms (it's nicer than it sounds) on Leera, an ocean world inhabited by frog-like aliens.
- In Everworld, Poseidon and Neptune both have underwater cities, and they're fighting over Atlantis. We mostly see Neptune's city, where water can be drained, or humans made amphibious, based on the god's whim. (This is not encouraging.)
Live Action TV
- The Man From Atlantis episode "Crystal Water, Sudden Death".
- In the first episodes of Stargate Atlantis, the city is discovered to be underwater, having been submerged by the Ancients to escape constant orbital bombardment from the Wraith. In a subversion of the Gone Horribly Wrong situation mentioned above, when the shield fails, the city surfaces.
- ORCA in Ocean Girl is halfway between this and Underwater Base. The ORCA City project may be closer to this trope.
- seaQuest DSV is set in a world where the ocean floor has been so heavily colonized that there are whole underwater nations.
- In the cartoon segments of The Aquabats! Super Show!, the band tries infiltrate an underwater city beneath the moon's surface to save Jimmy the Robot.
- In Star Trek: The Next Generation, still reeling from his recent assimilation by the Borg, Picard is briefly tempted in "Family" to quit Starfleet and join the Atlantis Project, who are aiming to build one of these on the floor of the Atlantic Ocean.
- Several Dungeons & Dragons settings include undersea civilizations of merfolk, tritons, sahuagin or the like; some of these use air-filled domes as housing for surface-dwelling visitors. The Known World/Mystara campaign setting has the Kingdom of Aquas, which was once part of the Empire of Alphatia.
- In New Horizon, Aquilon's Reach has multiple underwater cities, as well as some atop glaciers. Unsurprisingly, they also boast the best navy in game.
- See the Shadowrun, 2nd Edition supplement Portfolio of a Dragon: Dunkelzhan's Secrets; in his will Dunkelzhan left a bequest of 5 million nuyen to the first party to establish a self-sustaining community of at least 100 persons on the ocean floor. Yamatetsu Corporation eventually won the bequest with their SoaTome AquaDomes.
- Transhuman Space has Elandra, an Australian-founded "free city" under the Pacific. It's more of a town than a city, really, but a respectably-sized one.
- Underwater cities have cropped up occasionally in the lore of Warhammer 40,000.
- Mahri Nui in BIONICLE
- Rapture from BioShock is a Diesel Punk and Bio Punk city that's completely underwater, save for a lighthouse that contains a bathysphere to bring people down from the surface.
- The Dome of D'sparil from the last level of Heretic.
- The Call To Power series has sea cities.
- Area J from Mega Man ZX.
- Aquaria has Mithalas City, which has long since been completely ruined after a Path of Inspiration corrupted its patron deity into a horrible monster. Guess what you end up fighting in the ruined cathedral.
- In Mass Effect, it's mentioned that Kahje, the homeworld of the aquatic Hanar has 90% of the surface covered by water and features impressive domed cities, originally built them for the Drell after the Hanar rescued most of their species from their dying homeworld, two centuries previously.
- The main premise of Atlantis Underwater Tycoon is to build and maintain one.
- A new feature in the Rising Tide expansion for Civilization: Beyond Earth is the ability to build cities on ocean tiles.
- The Hylotl from Starbound live in these. And it looks awesome.
- In The Gamer's Alliance, Adlivun is a thriving underwater city populated by merfolk known as merrows.
- Futurama featured the Lost City of Atlanta.
- Sealab 2020 opening credits.
This is the year two thousand and twenty. The place is the Challenger seamount, the top of an underwater mountain, a complex beneath the sea. 250 men, women and children live here, each of them a scientist-pioneer. For this is our last frontier, a hostile environment which may hold the key to tomorrow. Each day these oceanauts meet new challenges, as they build their city beneath the sea. This is Sealab 2020.
- Sealab 2021
- ... not to mention the other Sealab featured on Centurions .
- The Superjail! episode "Superbar".
- Jonny Quest: The Real Adventures episode "Undersea Urgency".
- Atlantica from The Little Mermaid.
- They visited Atlantis on The Fairly OddParents. Also, Clevelantis.
- The main premise of Atlantis: The Lost Empire.
- King had Bubble Town, the capital of the nation of Undersea, ruled over by the despotic Cousin Tess.
- The Adventures of Super Mario Bros. 3 had one in the episode "The Ugly Mermaid". It was a bizarre case in that the city had domes with air in them, despite the merfolks not being able to breathe air.