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Alien Sea

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Dax: If you ask me, the seas could be a little more purple.
Kira: Funny, I was just thinking they weren't green enough.
Bashir: I guess it's true what they say. There's no place like home, no matter what color the water is.

One of the quickest, easiest ways to establish an alien world as being very unlike Earth is to make its "water" some wacky color, or give it some other unusual features or appearance. It's not always explained exactly what kind of chemicals or minerals are causing it to look this way, but regardless, it's still perfectly able to support the native flora and fauna (though that doesn't mean it is safe for Earthlings).

See also Alien Sky, which serves the same purpose and may accompany it — the Earth's oceans are the same color as the sky due to similar refraction, so if the sky and sea don't match you must be someplace exceptionally alien. Alien Landmass is another sister trope, often used for the same reasons.

Compare Waterfall into the Abyss. Contrast All Planets Are Earth-Like.


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    Anime & Manga 
  • Children of the Whales: The oceans are made up of sand rather than water, but come complete with waves, islands, phenomena such as waterspouts and whirlpools, and an abundance of marine life. Unlike water oceans, however, the sand isn't buoyant enough for people and boats to float on the surface without magical aid.
  • Dragon Ball Z: The oceans of Namek are green (and the vegetation is blue).
  • Neon Genesis Evangelion: Used in the movies:
    • By the ending of The End of Evangelion, the sea has turned into red-orange LCL, liquified human rests resulting from the Assimilation Plot, containing their merged souls.
    • In the Rebuild of Evangelion movies to highlight the ecological damage to Earth post-Second Impact: the sea has literally turned red with blood.

    Fan Works 
  • No stars in sight: At the start, Ikharos is exploring the surface of a Rogue Planet filled with seas of acidic chemicals that he speculates is some sort of primordial soup based on how the planet's only two complex lifeforms (alien slugs and lichen) lived on the rocks closest to these seas.
  • Sonic Runaways: Collision Chaos' sea is neon, purple in some areas and orange in others, and also in the sky.

  • Animorphs:
    • The Yeerk homeworld is covered with huge lakes of what look like melted lead, where the Yeerks live in their unhosted state.
    • Leera, meanwhile, is mentioned to have oceans so clear that you can see for miles, and lifeforms so bizarre a marine biologist would happily give up an arm to be there for an hour. Ax also suggests that it lacks predators, with geothermic energy pumping up to support everything.
  • The Cosmere:
    • Oceans in the Spirit World of the Cognitive Realm are composed of tiny glass beads, each of which represents an inanimate object in the Physical Realm. They're still deceptively easy to drown in.
    • The world of Lumar has oceans composed of colorful pollen dropped by the planet's twelve moons. Air blown up from vents below causes the spores to act like a liquid, enough so that ships can sail on them.
  • The Dark Artifices: The sea in Thule is stark black.
  • Dragaera: The series reveals in passing that the ocean is orange, although it's unclear if this applies to the whole thing or just the portion that's blanketed by the Overcast.
  • Domain: In Resurrection, Xibalba's seas and lakes are silver-colored.
  • The Elric Saga: The Heavy Sea that allows travel between worlds is thick like mercury. It's just barely drinkable but has to be chewed.
  • Expedition (and its adaptation Alien Planet): The Amoebic Sea is actually a living gelatinous colloid composed of immense colonies of microorganisms. The edge of the sea towers over the surrounding beach. It was formed in response to the drying of Darwin IV, which some of its aquatic microorganisms responded to by locking as much water as possible inside of themselves until their huge, gelationous colony was the only "water" left.
  • Hic Sunt Dracones:
    • The oceans around the Farlands are made from freshwater.
    • The Maw of Damnation is a small ocean in the middle of the Farlands Supercontinent that is almost black in color and notably bitter. It has very unstable weather, with storms appearing and disappearing with no rhyme and reason and is inhabited by particularly nasty sea dragons and sea monsters.
  • Humanx Commonwealth: The planet Quofum is best known for two things: being prone to disappearing and having oceans that are 9% alcohol.
  • Jackelian Series: The Fire Sea is a region of ocean underlain by intense volcanic activity, dominated by submarine-cooking Boils and fast-growing mutant corals that thrive on heat.
  • Joel Suzuki: The oceans on the planet Greenseed are green.
  • A Lord from Planet Earth: In the third novel, aptly named Sea of Glass, all bodies of water on a remote uninhabited planet appear to be made of dust or sand. In fact, the water is perfectly consumable and hydrating, but it only turns to liquid when ingested by someone, although it does feel a bit like eating sand at first. It's a strange curiosity that no one has bothered to study since humanity is too busy fighting a war with a Blue-and-Orange Morality enemy. The final Combat by Champion takes place on this planet on the shore of a "sand" sea. The protagonist manages to deliver the killing blow, and then both his and the enemy's blood mixes and contacts the "water", which starts a chain reaction that turns the entire sea into regular liquid water.
  • Manifold: Space: The Gaijin homeworld has a sea made of yellow, bubbling iron carbonyl and nickel carbonyl.
  • Monster Blood Tattoo, set in a bio-alchemical-punk fantasy world, has strongly acidic, multicolored oceans that are the result of exotic salts from the sea floor dissolving into the water. Swimming in it is unhealthy: in half an hour, you will have a really bad rash, and over an hour and a half will kill you. There there's the colossal monsters and kraulschwimmen that stalk the sea lanes and prey on ships and sailors.
  • Phaeton: Carbonia has seas of amniotic fluid-like material, which allows humans to breathe in them. Interestingly, the air is toxic to humans.
  • Railsea: In an especially weird example, the book is set in a world where the seas are dirt — fathoms-deep, unfarmable dirt — that throngs with oversized hyper-predatory versions of all manner of burrowing creatures. A sprawling, intertwining network of rail lines covers the surface of these "seas", and carries specialized trains which fulfill all the roles which ships might perform on a conventional ocean.
  • Revelation Space Series: Planets which are inhabited by Pattern Jugglers usually have most of the surface covered by oceans. Their water contains numerous microscopic organisms that give the water an unusual color and density.
  • Skylark Series: The planet Osnome has literally blue oceans. This is because they are an ammoniacal copper sulphate solution — copper being exactly what the protagonists are in search of.
  • Solaris depicts a strange planet completely covered by a multicolored sea, which is actually one living, sentient organism. There were two film versions of the book which also contained this sea.
  • The Space Trilogy: The waters of Malacandra have the peculiar quality of very pointy standing waves and are literally blue (not just reflective of the sky). The seas of Perelandra, on the other hand, are orange, and have floating mats of seaweed on which "land-dwelling" life grows instead of islands.
  • Starsnatcher: Shadowmoon's oceans turns pitch black just a few feet below the surface. This is a result of orbiting a red dwarf star whose infrared light has difficulties penetrating the water.
  • Tales of the Five Hundred Kingdoms: The Fairy Godmother: Elena and Alexander's Erotic Dreams take place on a "shore of purple sand by an amethyst sea" under an Alien Sky.
  • Xeelee Sequence: On the Core of Cores, there are oceans of some quasi-liquid material, thick and red as blood.

    Live-Action TV 
  • Doctor Who:
    • "The Keys of Marinus": Marinus has sands of glass and seas of sulfuric acid.
    • "Mindwarp" opens with the TARDIS landing on the beach on a planet where the ocean is bright pink.
  • Star Trek: Deep Space Nine:
    • In on scene, various characters compare the tint of the oceans on their homeworlds. Earth's are blue. Bajor's are green. Trill's are purple.
    • The Great Link resembles a reddish ocean, but it's actually billions of Changelings in liquid form, intermingling with each other.
    • "Past Tense, Part I": To Dax and Kira, Earth's blue sea is rather odd — Trill's ocean is more purplish, while Bajor's is more green.

    Tabletop Games 
  • BattleTech will occasionally have a note about an ocean, sea, or lake on a particular planet having a distinctive, exotic color. Usually because of the local marine microorganisms or unique mineral content in the water.
  • Blades in the Dark: The sea is ink-dark with occasional hints of star patterns.
  • Call of Cthulhu
    • Campaign The Fungi from Yuggoth, adventure "Halls of Celaeno". The fourth planet of the star Celaeno (in the Pleaides) has a grey ocean.
    • Fragments of Fear (second Cthulhu Companion), adventure "Valley of the Four Shrines". The Player Characters can use a Crystal Ball-like device to view the gray Lake of Hali where Hastur the Unspeakable lives (a planet circling the star Aldebaran).
  • Dungeons & Dragons
    • Adventure Q1 Queen of the Demonweb Pits. One of the alternate worlds the Player Characters can visit from Lolth's Web is a planet with a pink ocean.
  • Exalted: The sea of the demon realm of Malfeas is an intelligent, acidic, and very, very bitter Yozi named Kimbery, the Sea that Marched Against the Flame. According to some accounts, she is greater than every sea in Creation combined, and holds treasures and lore unending for those who are willing to scrape her acidic, benthic depths.
  • Planebreaker: The Sea of Uncertainty on the Planebreaker is filled with detritus, artefacts and creatures it's picked up as it crashes through the infinite planes. The substance making up the sea shares many physical qualities with water, but differs from water in that it appears red from a distance, does not relieve thirst, and is oddly buoyant. No matter how far someone swims down, the seafloor continues to extend farther downward, although the light never fades to darkness.
  • Rocket Age's Mars has silt seas, where the old seas of water slowly dried up and filled in as the planet's ecology collapsed.
  • Werewolf: The Apocalypse: Lady Yul's Malfean abode is a multicolored sea of toxins

    Video Games 
  • Evolva: The sea that appears during levels 9 and 10 is mentioned in the manual as being made of acid, and it proves it by being instantly lethal, should you dive into it.
  • Guild Wars: The Jade Sea is literally made of Jade due to Shiro transforming a normal sea with the Jade Wind. The waves are now frozen in place in the form of pure Jade as is the maelstrom known as Unawakening Waters. Bizarrely, fish such as kraken, carp, rays, jellyfish, and crustaceans still live on the Jade Sea's surface though have (with the obvious exception of crustaceans who already have legs) sprouted legs (carp and rays) or have taken to floating (kraken and jellyfish).
  • Iron Lung is set beneath a sea of blood on an alien moon. Note that the ocean is not bloodred, but actual blood.
  • Kerbal Space Program has Eve, with its purple oceans (which may be partially made of rocket fuel.) Averted with Laythe, which from some angles looks as if you might still be on Kerbin.
  • The Legend of Spyro: The Eternal Night: The seas around the Ancient Grove, and over which the Skavengers' pirate fleet flies, are the same vivid purple as its Grimy Water. Later, the sea around the White Isle is a bright, glowing aqua shade.
  • Mass Effect: Andromeda: The oceans of Kadara, as seen from orbit, are green. Also, if they're anything like the inland bodies of water, loaded with volcanic sulfur and pure poison to the touch.
  • Myst:
    • Multiple Ages — Spire, Relto, and Kadish Tolesa among them — have a 'sea' consisting of a thick layer of fog.
    • The 37th Age has a sea filled with "dark currents"; when the seawater mixes with the freshwater that flows from the rivers of the one charted island, it releases a thick mist which the inhabitants worship as The Whiteness.
    • Torus' twin "seas" are connected through the hole in the centre of the ring; driven by a force of unknown origin, the water on one side drains through an enormous whirlpool and into an enormous fountain on the other, where it gushes into the upper atmosphere, evaporates, breezes to the "edge" of the ring, and condenses and falls as rain.
    • Riven:
      • While never explicitly stated, the oceans of Age 233 are known to be highly acidic. For one thing, Gehn collects his water from a giant bowl on the roof. For another... well, try and guess the range of the tidal zone.
      • Riven has water that is more of a gelatinous colloid suspended in a mesh of microorganisms that are noticeably afraid of heat.
    • Uru: The enormous lake surrounding Ae'gura was filled with algae that caused it to glow in the dark 3/5 of the time, producing a day/night cycle. Until the algae were wiped out, of course.
  • No Man's Sky: Thanks to the 2018 Abyss update and the patch that followed it, the seas are filled with exotic alien marine life and the waters can be a wide array of colours.
  • Populous: Four of the terrains have differently-colored substances that function the same as water in the others: Rock & Lava has red lava, Bit Plaius has floating letters spelling BULLFROG, Cake Land has caramel, and Silly Land has a checkerboard pattern.
  • Shadow Man: There is no water in Deadside. Instead, you will wade through rivers, lakes, and waterfalls of blood.
  • Sonic the Hedgehog CD: The Special Stages are set on islands on other planets, each with a different color ocean.
  • Spore: Different planets' seas can be blue, green, or red.
  • Sunless Sea: The Unterzee is pretty strange. To start with, most of the water is a sinister dark green, with the main exception being the far south (where it mingles with the blood of an Eldritch Abomination and dissolves the hulls of ships). Various other areas are weird in new and interesting ways: the Sea of Voices, for example, has a seafloor made of moving faces, while Irem is unstuck in time and the entire northern side is arranged so that if you go off the map you invariably pop up at either Frostfound or the Avid Horizon with no idea how you got there. This is to say nothing of areas like the Iron Republic, where the zee's already loose application of the rules of reality is being intentionally undermined by Hell.

  • Homestuck:
    • The lakes and seas of John's planet, the Land of Wind and Shade, are made entirely of tar.
    • Rose's planet, the Land of Light and Rain, is covered in iridescent oceans whose surface is colored in a swirling mottled pattern of blue, gray, pink and yellow.

    Web Original 
  • Goodbye Strangers: The Flooded Future World shown in the Walltown and Infrared modules is covered in red water.
  • The various Lands in Homestuck feature rivers and seas made of things like magma, oil, blood, paint, and tea.
  • Orion's Arm has quite the variety, depending on the type of planet. There are seas of oil and tar, dilute hydrochloric acid (and these also tend to be quite shallow, due to high gravity of such planets), sulfuric acid and lava.
  • SCP Foundation, SCP-2264 ("In the Court of Alagadda"). The city inside SCP-2264 is surrounded by a black ocean. The nature of the liquid is unknown but it appears to be more viscous than water.
  • Serina: Downplayed. The moon's oceans are largely similar to the ones of earth but a vast amount of phytoplankton in the water gives it a greenish tint. There's also the fact that when compared to earth, more of serina's oceans consist of shallow seas which allows a greater abundance of aquatic plant life and by extension, a more diverse array of animal life.

    Western Animation 

    Real Life 
  • Saturn's moon Titan has black seas composed of a mix of ethane and liquid methane rather than water, and reflect the orange-brown sky. Needless to say, it is not an environment that would be well suited for human life.
  • Jupiter's moon Europa and Saturn's moon Enceladus are both suspected of having massive oceans hidden under miles of surface ice.
  • Earth can give the impression of not being itself in places, too:
    • Lake Tahoe is noted for its unusual color. The water appears to change from gold to green to blue to purple depending on the depth.
    • Similarly, Emerald Bay.
    • The Laguna Colorada in Bolivia is a red lake. No, really.
    • Ho'okena Beach on Hawaii's Big Island is one of the few gray sand beaches in the world.
    • Morning Glory Pool in the Yellowstone National Park used to be an example. It had originally been rainbow-colored because of special bacteria that lived in the hot spring water, but because visitors threw trash into it which clogged the natural hot water entries, its color is slowly fading, with estimations that it will soon be just another common hot spring.
    • Elsewhere in Yellowstone, the Grand Prismatic Spring is also rainbow-colored and the largest hot spring in the United States.
    • There is also the Lake Retba or Lac Rose in Senegal and this lake is pink. The color is caused by strange bacteria and, oddly, salt content.
    • The mountain Kelimutu as three lakes on its top, each with a different color: one is black, one is turquoise and one can range from red to blue depending on the minerals in it.
    • The Blood Falls of Antarctica, which is a crack in a glacier out of which a large sea of dark red water is flowing, making the glacier look like it's bleeding. The coloration is due to the micro-organisms which live in the water, which have been frozen for millions of years inside the glacier.
    • In certain areas, large amounts of glass are worn smooth by erosion and washed to shore to form "glass beaches," entire beaches covered in what looks like many-hued and colored rocks. The most well known of these is Glass Beach, but it's far from the only example.
    • The "hypersea" theory of paleontologists Michael and Dianna McMenamin attests that the body fluids — blood, endolymph, sap, cytoplasm, whatever — of eukaryotic land organisms can, in effect, be considered a highly-compartmentalized extension of the oceans. Like seawater, the liquids comprising terrestrial life are solute-rich, churned by seasonal "currents" (migration) and "upwellings" (rising sap in trees), and inhabited by untold millions of specialized life forms (pathogens and parasites) to which a host organism's body is just another aquatic habitat.
    • Bioluminescence makes sea glow in the dark.
  • In the 80s and 90s, paleontologists asked themselves: what were the ancient seashores like? Real ancient, pre-Cambrian and early Palaeozoic. Current consensus is that without higher plants, erosion from wind and water was very rapid, and land was very flat low plains with occasional vertical rocks. There was no such thing as riverbeds; water flowed into the seas as an even layer all over the shoreline. Sediments were carried far into the sea, resulting in far stretches of shallow waters. There was no distinct border between sea and dry land, no shoreline, just kilometres of shallow pools and mud, that got slightly wetter at high tide. Creatures like modern mudskippers would thrive in such environment. Even in the deeper areas, a great deal of iron was suspended in the water, turning it a sickly green color. It wasn't until certain unicellular organisms began producing oxygen as a waste product that the iron content of the oceans dropped considerably (due to the oxygen binding to it, turning it to rust), leaving them their current blue hue.
  • As explained on the Alien Sky page, the color of the daylight skies of other planets vary depending of the type of star they're orbiting. As oceans reflect the color of the sky, this mean a habitable zone-planet orbiting a star hotter than the Sun would have even bluer oceans than ours and conversely if said star was cooler its oceans would look from a washed-out blue to white and even orange.
  • The oceans of lava theorized to exist in planets that orbit very close to their stars such as CoRoT 7-B or Kepler-78b.
  • Venus can be said to be covered in a sea of supercritical carbon dioxide thanks to its large atmospheric pressure and hot temperature.
  • Last, but not least, for something really alien the global oceans of metallic hydrogen that form the bulk of Jupiter-like planets, or especially the oceans of liquid diamond with bergs of diamond too, that likely exist in the depths of Uranus, Neptune, and similar planets.