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Apparently Human Merfolk

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"At thirty, the prime of a mermaid's life, her tailfin splits in two so she can live on land. Mermaids are a mysterious species."
Kokoro, One Piece

So you have mermaids and -men, half-human half-fish (or part seal, dolphin, whale) who come with their own set of problems. Then you have Fish People who are humanoid but scaly; think of the Creature from the Black Lagoon.

Then there's these characters. They look so human that they could wander unnoticed down a city street, but can breathe and live underwater. In fact many prefer to live underwater as that is often where they were born, and they only come to the surface to complain that Humans Are the Real Monsters for polluting the ocean, or to do some superheroing. In fact if they are unused to life on land they may find themselves acting like a Fish out of Water.

This can include anything from an individual who has this ability as a special quirk, to whole civilizations of these who may or may not live in an Underwater City.

Often overlaps with Walk, Don't Swim, Water Is Dry, and Water Is Air. Compare Human Aliens, where "alien" species look exactly like humans do, yet count as aliens. Subtrope of Our Mermaids Are Different. See also Captain Fishman.


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    Anime and Manga 
  • The Ragnans of Macross Delta have shark-like gill slits on the base of their necks, webbed hands and feet, and fins on their elbows and calves.
  • Not the mermaids themselves, but the Panthalassa race in Mermaid Melody Pichi Pichi Pitch is composed of these. Most of them, however, don't have a choice but to live underwater (until the seal on their civilization breaks, that is), and we only see a few of them, many of whom we're supposed to assume are human until we realize that they've survived instances where they should have drowned. They also have nebulous, unexplained superpowers and crosses. Huh.
  • The people of Shioshishio in Nagi-Asu: A Lull in the Sea look exactly like regular humans except for ocean-blue eyes and a nearly-invisible scaly skin coating that allows them to breathe underwater. They can breathe out of water equally well, but have to periodically soak in seawater so their skin doesn't dry out. Despite the fact that the mer-people and land-dwellers look nearly identical, Fantastic Racism abounds in both directions.
  • When mermaids in One Piece turn 30, their tail splits into legs. They can turn their legs back into a tail if they need to, but seems to default to a form indistinguishable from humans.
  • Squid Girl: Arguably the eponymous character, since when she isn't manipulating things with her tentacles, she appears to be a normal girl with a hat and a weird hairstyle.
  • Umi Monogatari is the story of two sea people (with pointy ears and internal gills, but otherwise human) who take a trip to an island to return a ring. They aren't spotted as mermaids at all, which causes... problems.

    Comic Books 
  • In Cavewoman: Deep Water, Meriem fights an apparently human merwoman (albeit one with an unusual skin tone if the cover is to be believed). Her exact motivations are murky, and a rematch in the future seems likely.
  • The DCU has Aquaman, Mera, Aqualad, Clea and their kin. Somewhat of a mixed example, as Atlantis also includes more traditional mermaids (Lori Lemaris, Ronno) and others (Lagoon Boy, Blubber) who are animal/sea-life mixtures.
  • Fathom is about a member of a race of water-based humanoid Elemental Shapeshifters who have this among their abilities.
  • The Marvel Universe has Namor the Sub-Mariner, who has slightly pointy ears and wings on his feet as he can also fly but looks much closer to human than fish. Namor's people also normally have blue skin, but he's half-human and a mutant to boot (hence the wings, which are not natural to either side of his lineage).
  • The Aqualanians from Swordquest: Waterworld are a race of undersea merpeople; aside from their yellow-green skin and green hair, they look like humans (complete with legs) and are capable of breathing air.

    Film — Animation 
  • The plot of the anime movie Coral Reef Legend: Elfie of the Blue Seas has main protagonist Elfie as one of these and the last of her kind, as all her people were exterminated years ago.
  • The Little Mermaid II: Return to the Sea: Melody is physically a human despite her mermaid heritage from her mother's side, and even before Melody turns into a mermaid, she can swim faster and hold her breath underwater longer than the average human. However, this is downplayed since Ariel lived as a mermaid for most of her life before permanently becoming a human.

    Film — Live-Action 
  • Atlanteans as seen in Aquaman (2018) are visually indistinguishable from humans. Internally they are very different. They have all of the Required Secondary Powers needed to thrive underwater: modified lungs adapted for water breathing, a thicker skin to withstand deep sea pressure and cold (and surface weapon attacks), and being able to see in the dark. This is thanks to the power of the Trident of Atlan which altered their physiology even as the ill-advised attempt to weaponize it sunk Atlantis. The high-born Atlanteans such as Arthur himself are also capable of breathing air (the rest of the Atlanteans need Powered Armor filled with water to survive on the surface). It's worth noting that the present-day Atlanteans are only one of the Seven Kingdoms. The other Kingdoms are populated by the descendants of other survivors of Atlantis who made their homes in less hospital parts of the sea, and over the course of generations they stopped playing this trope straight. One kingdom became Fish People, another became Crab People, and another became... monsters.
  • In Chelovek-Amfibiya (The Human Amphibian), an oceanologist's son with sick lungs is given additional implants derived from the gils of a young shark. He can survive on land, but mostly sticks to the sea, where he's more comfortable with breathing. The main plot point of the movie is the gradual deterioration of his ability to breathe atmospheric air and the need to forever leave dry land and live purely in the sea.
  • At the end of Splash, Allen becomes one of these so he can be with the more typical mermaid love Madison.
  • The Mariner in Waterworld has gills behind the ears, apparently the result of a mutation.
  • In Black Panther: Wakanda Forever, Namor's city of Talokan is full of merfolk. During the Spanish conquest of South America, some Mayan villagers suffering smallpox prayed to the rain-god Chaac for help, and their shaman found a glowing blue plant in their cenote. After he made a drink for everyone, it gave them gills and turned their skin blue so they could escape into the ocean; underwater, their skin turns brown again. The plant's mutating abilities is because several millennia ago, a meteor full of vibranium fell to Earth and landed off the coast of the Yucatan Peninsula.

  • Aquiliton by Maureen Myers features two kinds of merpeople: the traditional kind with fish tails and ones who completely resemble humans and can breathe air, but they'll dry out and die if they stay on land too long and tend to have pale skin and big feet. Also, females develop a sort of charm power during puberty that is replenished by moonbathing. The human-appearing merpeople can interbreed with humans, but their offspring usually die young.
  • Electra of the Not Quite A Mermaid series was born human but was found after a storm by merfolk and given magical sea powder so that she could breathe and live underwater.
  • The titular character of Percy Jackson and the Olympians, what with him being a demigod son of Poseidon and all, can breathe water as easily as air (with his lungs).
  • The rifters from the Rifters Trilogy are modified humans (cybernetics and genetic engineering are used) who can survive in deep sea conditions. In fact, they prefer the sea to staying in their confined Underwater Base.
  • The Secret of Platform 13 has Melisande, a nymph who continually points out her feet, for some reason touchy about the idea that people will mistake her for a mermaid.
  • In The Voyage of the Dawn Treader, Lucy views these sorts of Sea People through the crystal-clear waters of the eastern Last Sea. They don't make contact, but she watches them using trained fish like hunting falcons and observes underwater farms and a royal court.
  • Siren: Sirens look exactly like humans, except for their silver eyes.
  • In Soon I Will Be Invincible, this is implied to be the case with Damsel's mother, an alien princess who married her superhero father.

    Live-Action TV 
  • The 4400: In "The New World", Jung Pak, who disappeared in 1956, develops gills on his back.
  • The Boys (2019): The Deep appears completely human at first, but is later shown to be one, with gills on his torso.
  • An episode of Dark Angel has a couple of transgenics who look perfectly human except for the gills coming out of their backs and their inability to speak. They also lay eggs.
  • Man from Atlantis: The only indication of the eponymous man's nature is his webbed hands.
  • The third season of Mighty Morphin' Power Rangers introduces the Alien Rangers, a race called the Aquitians who live on an ocean planet. As far as their appearance goes, they're more Rubber-Forehead Aliens who speak with voices that sound like they were put under an underwater distortion filter.
  • The titular heroine of Ocean Girl looks fully human, despite being able to swim much faster and stay underwater for far longer.
  • The Outer Limits (1995): In the episode "The New Breed", a scientist is injected with nanomachines which "correct" his cancer and myopia. When he and his friend test the limits of the nanites' abilities, one of the tests is to see how long the man can stay underwater. The nano-robots misinterpret this by giving the man gills so he can breathe, seriously squicking him out.
  • In later seasons of SeaQuest DSV, the character Tony Piccolo is a human who was modified with gills along his sides (and probably Required Secondary Powers to allow him to survive deep-sea pressure) but otherwise looks completely normal.
  • Marina and her people (all of whom are mute) from Stingray (1964).

  • Classical Mythology:
    • Unlike many modern depictions which depict him with a fish tail, Poseidon looked entirely human, and in many Archaic and Classical-era depictions virtually indistinguishable from either of his brothers, Zeus and Hades.
    • Female water nymphs such as Oceanids, Nereids, and Naiads look invariably entirely human (though perhaps more beautiful than mortals). Potamoi, the male spirits of rivers and the brothers of the Oceanids, were sometimes also depicted as human (with horns). Other times they were depicted as bulls with human faces, because rivers were said to be bull-like in nature.
    • Depictions of sea gods like Nereus and Proteus in Classical iconography vary between looking entirely human or with a long, serpentine fish tail in place of legs, depending on the context or preference of the artist.
  • This is the typical form of mermaids in the Arabian Nights and other Middle Eastern folklore; the only difference between them and land-dwelling humans is that they (and in one story, their children with humans) can breathe underwater.

    Tabletop Games 
  • Blue Planet: The Aquaforms engineered for colonizing Poseidon look human for the most part, just with webbing and gills ("squids") or expanded lung capacity ("divers").
  • The Stormwrack source-book for Dungeons & Dragons 3.5 has aventi, who, in a justified version of this trope, are actual aquatic humans. They were once a great empire who sunk beneath the waves during a cataclysm, but their god mutated their bodies to be able to survive underwater. Apart from a few distinct features, such as unusual colored hair and skin tones, and fins on their wrists and ankles, they are pretty much identical to humans, and the book explicitly states they can easily disguise themselves as such.
  • The aventis' Pathfinder counterparts, the gillmen, are formerly-human survivors of the destruction of Azlant by meteor. Some of these survivors were abducted by Azlant's aboleth masters, who subjected them to fleshwarping that gave them gills and a psychic weakness to the aboleths' mind control. While they look mostly human from a distance, the gills on their neck and their purple eyes (common to all Azlanti) give them away. They also must soak themselves in water every 4-24 hoursnote  or risk death by dehydration.
  • Traveller: The Nexines who actually are human merfolk. They are a race genetically engineered for underwater mining. Their name is like the name Nexie, which is a kind of water fay.

    Video Games 
  • Aquaria has Li become this shortly after Naija finds him. It's a handy side benefit of your Fish Person girlfriend having magic powers, though it might only work if they're in close proximity — Li puts his old diving helmet back on if Naija decides to leave him behind somewhere. Their son might also count.
  • In Arknights the Aegir race are a seadwelling race with characters associated with various sea creatures. Unlike the other Little Bit Beastly races, the Aegir look like normal humans, with their associated species being confined to clothing motifs. This also applies to the members of the Abyssal Hunters, who are heavily implied to be Aegir, but it's unstated due to their Mysterious Past.
  • Perfect World:
    • The Tideborn people look mostly human-like except for prominent gill-flaps where humans have ears, pale blue or purple skin, and prevalence of white and gray hair colors in all ages (as well as other unusual hair colors). Player characters assume a more traditionally merpeople-like shape when they meditate to recover health and mana, and Tideborn who attain very high levels of magic power frequently have fins on their limbs or crustacean-like limbs extending from their backs.
    • The sprites used to represent Little Leaf and the murdered Little Yetz, two daughters of a Tideborn mother and Earthguard father, suggest that dominant genetics favor the Tideborn colorations, as well as the Super Not-Drowning Skills alluded to in the story text, in the event that Tideborn should breed with members of other races.
  • In Soul Nomad & the World Eaters, the Nereids are a pretty clear example with a female One-Gender Race bonus as well. There are some minor differences, though; they have blue skin and hair, and small breasts so as to swim through the water better. They also have to mate with humans (or possibly Sepp, this isn't ever made clear) to produce offspring, too. Their leader is a more traditional mermaid, but this is never given an explanation.
  • The Inklings and Octolings from Splatoon look mostly human while they are not on squid form; the only things that make them stand out are pointy ears, unnaturally-colored hair that looks like tentacles and having fangs in their mouths. Unlike most examples in this trope, however, they can't swim in water. They can only swim through ink (and only if it's the same color as they are).
  • In Tales of Legendia, the Ferines are an aquatic race that looks perfectly human despite the fact that they evolved completely underwater; their planet had NO dry land until humans from space came and raised it from the ocean.
  • Naiads in The Witcher walk literally naked (yes, right in the game, with all the details), have greenish skin and dark green hair (yes, pubic hair too), but otherwise absolutely human. Dryads and Lady of the Lake closely resemble them in appearance, except that Lady's best parts are covered with her long hair.

  • The seatrolls of Homestuck look exactly the same as any other troll except for having fins attached to their cheeks. (Fans sometimes depict the fins as coming out of their ears instead.)

    Western Animation 
  • SpongeBob SquarePants gives us Mermaid Man and Barnacle Boy, parodies of Adam West-era Batman and Robin as well as the Filmation Aquaman cartoon. They look like humans wearing superhero costumes (at all times) but can breathe and live indefinitely underwater and talk to sea creatures. The show eventually explains that they are normal humans. The starfish Mermaid Man wears on his face magically keeps him alive and was a gift from some friendly mermaids (hence the name). Likewise, Mermaid Man gave Barnacle Boy the ability to breathe water... by forcing him to ingest a bunch of barnacles.
  • In Sweet Sea, unlike his wife and children, who have mermaid tails, King Neptune has human legs.

  • The "aquatic ape" hypothesis argues that the "missing link" in human evolution involved a period when humanoid primates adapted to the sea like seals before returning to land, and that these evolved into modern humans. According to the hypothesis, this explains various human features like bipedalism, webbed fingers, and lack of body hair, arguing that humans themselves are merfolk that evolved to live on land again. Initially proposed by Alister Hardy in 1930, the discovery of hominid fossils in East Africa eventually disproved it, though it still has a small number of supporters.