Breathable Liquid

Don't worry, that's not urine.
It wouldn't be breathable if it was.

On occasion, a work has a reason for characters to breathe a liquid rather than the normal air. This has been accomplished with perfluorocarbon for medical purposes, and has been proposed with other theoretical substances to help with crushing pressures or high-g forces.

In fiction, Water Is Air tends to be in effect, as being able to breath in a liquid somehow lets you do other things the same as if in air, like talking normally.

Super Not-Drowning Skills is when a character is able to breathe ordinary water for no explicable reason. May be a component in an Artificial Gill.

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Examples:

Anime & Manga

• Bang Brave Bang Bravern!: In Episode Three, "Lulu... That's Her Name", Bravern fills his cockpit with a breathable liquid in preparation for combat underwater. He directly compares it to the scene from The Abyss, but the liquid covers Isami's mouth before he can finish asking how an alien robot from space knows what The Abyss is.
• Dandadan: One alien species are like human-sized mantis shrimp that have lungs instead of gills because they evolved in some sort of oxygen-rich liquid.^note The name for the liquid was in untranslated Starfish Language, but Okarun theorizes it's some kind of perfluorocarbon. This makes visits to Earth awkward, as they're adapted for underwater movement but can't breathe underwater or hold their breathe long. And when they bring a cow to their planet to milk it, it's very difficult because the milk dissolves in its surroundings.
• Neon Genesis Evangelion: The cockpits of the titular Humongous Mecha are filled with an oxygenated liquid called LCL which is required for the pilot to mentally sync with an Evangelion, as well as providing direct oxygenation of their blood and dampening the impacts from battle. Once the cockpit is flooded, the LCL is ionized, bringing its density, opacity, and viscosity close to that of air.
• Queen Millennia: The Insecta-type ships feature cockpits filled with liquid used for synchronization. Hajime opting to not pilot completely naked makes the ship lose control. He still goes off-source even when naked.

Comic Books

• The Incredible Hulk: How useful it is (or whether or not he has it at all) is Depending on the Writer, but ever since the early 2000s, the Hulk officially has the capacity to breathe underwater because he "evolved" an organ that fills his lungs with a breathable fluorocarbon liquid.

Film — Animation

• Doraemon: Nobita's Drifts in the Universe has the gang being accidentally caught in the Space Knights' vessel and taken away from earth, before the Space Knights decide to bring them back in a journey that will last for days. When the team's Bathing Beauty, Shizuka, asks if the Knights have a bathroom on their ship, Freya from the Knights reveals they do — a literal sphere of liquid that they can breathe inside while washing themselves.

Film — Live-Action

• The Abyss features a character using liquid breathing to dive thousands of feet without compressing. The film also features a scene with a rat submerged in and breathing fluorocarbon liquid, filmed in real life, no special effects.
• Mission to Mars: The ship that Jim gets into to fly to where the Martians ended up has some sort of breathable liquid in it.
• Oblivion (2013) mentions this in passing. When Julia wakes up from her cryosleep, she starts puking to which Victory comments "It's breathing fluid. Just let her get it out."

Literature

• In The Dark Forest, ships fill their cabins with breathable "Deep Sea Fluid" to protect their insides from the effects of hypergravity.
• Dark Life has "Liquigen" short for "Liquid Oxygen", which works similar to the fluorocarbon liquid mentioned in The Abyss above but has the advantages that it turns to vapor quickly when exposed to oxygen (good for when the driver stops using it — prevents them from needing to puke it up) and somehow prevents the human body from being affected with such things as the bends.
• Deeplight: Humans can breathe Undersea water. Since it's essentially liquid fear, the experience is not pleasant. Side effects include experiencing the terror of shipwreck victims as they drowned.
• The Forever War describes liquid immersion and breathing in great detail as a key technology to allow space travel and combat with acceleration up to 50 G.
• Ben Bova's novel Jupiter features a craft in which the crew is suspended in a breathable liquid that allows them to survive in the high-pressure environment of Jupiter's atmosphere.
• Known Space: One of the stories in the Man-Kzin Wars sub-series, In the Hall of the Mountain King, features a Tnuctipun pilot encased in a capsule of breathable fluid to protect him (and his normally air-filled lungs) from high-G maneuvers.
• In The Lost Symbol, Robert Langdon (the protagonist) is completely submerged in breathable liquid mixed with hallucinogenic chemicals and sedatives as a torture and interrogation technique by Mal'akh (the antagonist). He goes through a near-death experience when he inhales the liquid and blacks out, losing control over his body, but is soon revived.
• Hal Clement's 1973 novel Ocean on Top portrays a small underwater civilization living in a 'bubble' of oxygenated fluid denser than seawater.
• In Mary Lowd's Otters in Space series, the Jolly Barracuda fills with liquid "oxo-agua" when underway, allowing the crew to handle greater g-forces than most other spaceships — too bad nobody told the feline passenger.
• In the young adult novel Space Winners by Gordon R. Dickson, Peep is an alien from a high-gravity planet. When he falls off a boat in the middle of the ocean, he is too dense to float or swim, but his lungs are so powerful that he has no trouble breathing the water like air and just walks along the ocean floor to the nearest land.
• Star Trek: Federation explains that before the invention of the inertial dampener, the stresses of high-G acceleration required starship pilots to be immersed in liquid-filled capsules, breathing an oxygen-rich saline solution to prevent their lungs from being crushed.
• The sliph from the Sword of Truth series is a magical construct used by ancient wizards for rapid travel. She is composed of what looks like living quicksilver one must breathe while traveling (instantly lethal to anyone not possessing the appropriate magic).
• In Uplift, the Streaker, a starship crewed primarily by uplifted dolphins, is largely flooded with "oxywater" that the neo-fin crew can breathe without periodically leaving their stations to come up for air. They strongly prefer air, though.

Live-Action TV

• 7 Days (1998):
  • In season 1, episode 13, chrononaut Frank Parker is seen breathing a hyper-oxygenated perfluorocarbon liquid that is pumped through a sealed full body suit that he is wearing. This suit and liquid combination allow him to board a Russian submarine through open ocean at a depth of almost 1000 feet. Upon boarding the submarine, he removes his helmet, expels the liquid from his lungs and is able to breathe air again.
  • The three aliens that crashed at Roswell in 1947 are kept in alien jars at Neverland. One is still alive, and it can apparently breathe the liquid since it's not hooked up to any tubes.
• In an episode of Eureka, Sheriff Jack Carter is submerged in a tank of "oxygen-rich plasma" to be cured of the effects of a scientific accident.
• UFO (1970):
  • The aliens have (stolen) human bodies and stay inside spacesuits filled with an oxygenated liquid that cushions their bodies during faster-than-light travel. The liquid gives them a green tinge which is implied to be responsible for another trope.
  • Played with in the episode "Ordeal". Aliens kidnap Paul Foster and force him to breathe the liquid so he can survive being transported to the alien home world, but it turns out to be All Just a Dream.

Tabletop Games

• Hollow Earth Expedition: In the seas around the Sunken City in the supplement Mysteries of the Hollow Earth can be found crystal orbs that, when broken, oxygenate the surrounding water enough for land creatures to breathe it.
• Shadowrun: The "Cyberpirates!" Sourcebook introduced the Liquid Breathing Apparatus that has allowed divers to achieve depths down as far as 3,000 meters, as the liquid system completely negates the risks of decompression.

Video Games

• Banjo-Tooie: In Jolly Roger's Lagoon, Mumbo can cast a spell to oxygenate the local water, making the vast underwater sections of the level much easier to navigate. In all other levels, Banjo is at the mercy of an Oxygen Meter.
• Brigador lore states that Spacer vehicles are piloted by having the pilots submerged in "gel", a breathable gel-like substance which allows them to link themselves to the vehicle's systems, a much more advanced — and also, to them, less savage — method of implementing a Brain/Computer Interface than attaching neural jacks to their heads.
• In the EVE Online universe, pilots in capsules (escape pods that function as the control center for the spacecraft) breathe an oxygen-rich, nano-saturated, breathable glucose-based suspension solution.
• In Sword of the Stars, the Liir use a hyper-oxygenated liquid on their ships. The ceremony for joining the Black Swimmers includes a ritual "drowning" in the substance.
• X-COM: Terror from the Deep: "Aquanauts" fighting deep ocean conditions breathe a dense oxygen-carrying fluid.

Webcomics

• Invoked in Outsider. As Beryl, Tempo and Jardin are boarding a shuttle to take Jardin to a Loroi outpost, Tempo mentions that the shuttle is big enough to support inertial dampers, meaning that they won't have to use a liquid breathing medium to compensate for its acceleration.
• Played With in Tower of God. Instead of air, the Tower contains a substance called Shinsoo. Shinsoo is a substance that can act as both water and air, based on density and concentration. At lower floors the Shinsoo behaves more like air, while at higher floors it behaves closer to water. It's still breathable regardless, provided you can withstand the increasing Shinsoo pressure each floor provides.

Western Animation

• Captain Simian and the Space Monkeys: In the 23rd episode titled "Surf Monkeys Must Dive!", the crew are shot down by a militaristic society on a planet in danger of core destabilization and crash land in it's pink oceans, leading to their ship filling up with it's contents. Thankfully, the oceans are made up of an "oxygenated fluorocarbon", allowing them to breathe and even talk, albeit partially garbled.
• The Magic Key: The water in “Underwater World” is breathable due to magic.
• In an episode of Metalocalypse, the other members of the band submerge guitarist Toki in a "liquid oxygen isolation chamber" while recording an album in the Mariana Trench.
• In the Rick and Morty episode "The ABCs of Beth", we learn that Rick created a pocket dimension called Froopy Land to entertain his daughter. When she realizes that she didn't imagine it in adulthood, she accuses him of being careless. To prove her wrong, he throws himself off a cliff, revealing that everything is like a trampoline. Then he tries to drown himself, revealing that the water is breathable.
• Steven Universe: In a clear homage to Neon Genesis Evangelion, Peridot's Escape Pod fills up with some sort of liquid that humans can breathe through — which is quite strange when you consider that gems don't need to breathe.

Real Life

• There have been some experiments in liquid breathing using perfluorocarbon, which has a higher oxygen capacity than blood. It requires mechanical assistance to circulate the fluid, and often surgery to ventilate it, but liquid breathing has been used occasionally to help premature infants and adults with ARDS breathe since the 1990s.

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