20 of the Most Fascinating Sea Monsters from Mythology and Fantasy Fiction

It wouldn’t be a proper sea monster list without touching on at least a few of the squamous entities that dwell beneath the waves in the stories of H.P. Lovecraft. Cthulhu is probably the Old Gent’s most famous creation, described by Lovecraft himself as resembling “an octopus, a dragon, and a human caricature.” According to Lovecraft’s work, Cthulhu “waits dreaming” in his house in the sunken city of R’lyeh, but when he wakes up, there’ll be trouble. 

While Cthulhu may be Lovecraft’s best-known sea monster, he is by no means the only one. An actual deity from ancient times, Dagon is not only mentioned in some of Lovecraft’s most famous stories—the “Esoteric Order of Dagon” plays a major role in “The Shadow Over Innsmouth”—but also has a story of his own named after him and lent his name to Stuart Gordon’s 2001 Lovecraftian film, despite that movie sharing more in common with “The Shadow Over Innsmouth” than it does with Lovecraft’s story “Dagon.” 

Beginning in 1954, Toho created a sort of cottage industry releasing films starring their home-grown giant radioactive monster, Godzilla. Over the years, Godzilla went up against many threats, several of which came out of the ocean. Heck, Godzilla himself is technically a sea monster. But for a sea monster list, why not go with the creature that lent its name to the 1966 film Godzilla Vs. the Sea Monster. 

In the movie, Ebirah is a giant crustacean controlled by an evil organization known as Red Bamboo. Ebirah later reappears (thanks to the magic of stock footage) in All Monsters Attack and then later in Godzilla: Final Wars. Ebirah is superficially similar to the monster Ganimes, a mutated stone crab that appears in the 1970 film Yog: Monster from Space (aka Space Amoeba). 

In the 50s and 60s, Stan Lee and Jack Kirby populated the pages of comic books with a lot more than just some of their greatest superheroes—they also filled them with lots of big, lumpy monsters, many of whom came out of the sea. Few of these sea-faring brutes, however, are as memorable as Giganto, actually the name of a whole race of giant whales with arms and legs who helped the Atlanteans attack the surface world, beginning in Fantastic Four #4, published in May of 1962. 

Sea monster names can be confusing, and the Kraken is a prime example. The word comes to us from Norwegian, where it means an “unhealthy or twisted animal,” but it entered the popular lexicon when it was borrowed for one of the main antagonist monsters in Ray Harryhausen’s Clash of the Titans. While Harryhausen’s Kraken was a humanoid sea monster with tentacle-like arms and a fishy tail, the mythological Kraken more closely resembles a giant squid. The second Pirates of the Caribbean movie featured a more mythologically-accurate depiction of the Kraken, while the 2010 remake of Clash of the Titans boasted a critter that was something of a mixture of the two, also incorporating some crab-like elements. 

The version of the Kraken that shows up in Clash of the Titans may have been inspired by the mythological Cetus, taken from the Greek word kētos, meaning a large fish or sea monster. When Queen Cassiopeia pissed off Poseidon by claiming that she and her daughter Andromeda were more beautiful than the Nereids, sea nymphs who accompanied Poseidon, he punished them by sending the sea monster Cetus to attack Aethiopia. 

The King and Queen consulted an oracle and were told to sacrifice Andromeda to the monster in order to spare their kingdom. They chained her up to a rock, but she was saved when Perseus slew Cetus—in some versions of the story, he did this using Medusa’s head. Certainly sounds a lot like the Kraken of Clash of the Titans. Cetus later lent its name to a constellation and also showed up to menace Sinbad’s crew in the animated film Sinbad: Legend of the Seven Seas. 

There are loads of giant (and not-so-giant) sea monsters populating the movies, from the giant octopus of It Came from Beneath the Sea to more recent creatures like those in, say, Mega Shark versus Giant Octopus. But one of my favorites is the thing that attacks the Argonautica in Stephen Sommers’ 1998 Aliens-like, Deep Rising. While one of the characters within the movie hypothesizes that the creature is an evolution of a type of Cambrian worm known as an Ottoia, the end result is something more closely resembling the mythical Kraken, mentioned above.

Something of a matched set, Scylla and Charybdis also come to us from Greek mythology, specifically the Odyssey. Two monsters dwelling on either side of the Strait of Messina, Scylla represented the dangers of the rocky shore, and was depicted in a variety of ways, including as a woman with a dragon-like tail and dog heads sprouting from her body, while Charybdis represented a deadly whirlpool. The two monsters have given us an idiom that dates to this very day, with “between Scylla and Charybdis” meaning about the same thing as “between a rock and a hard place.” 

Famed for luring unwary sailors to smash their ships upon the rocks, the sirens are known for their lovely and enchanting songs, with which their names have become virtually synonymous. In Greek mythology, the sirens plagued both Jason and the Argonauts and Odysseus on their respective voyages. Most depictions of the sirens show them as part-woman, part-bird, though some more recent variants have taken a looser approach, as in the 2003 animated adventure Sinbad: Legend of the Seven Seas, in which the sirens are portrayed as a sort of living water taking on humanoid form. 

In Disney’s 1940 animated feature film version of Pinocchio, Geppetto and Pinocchio are swallowed by a sea monster named Monstro, who is portrayed as a giant sperm whale. In Carlo Collodi’s original 1883 book The Adventures of Pinocchio, however, that role is filled by the Terrible Dogfish, a giant ocean monster also known as “the Attila of fish and fishermen.” 

According to Collodi, the shark-like Dogfish is larger than a five-story building and has three rows of teeth in its enormous mouth, which is plenty big enough to swallow ships and, of course, Pinocchio and Geppetto.

In Norse mythology, Jörmungandr is also known as the Midgard Serpent because it is so long that it wraps all the way around the world and can hold its own tail in its mouth. The offspring of Loki and a giantess named Angrboda, when the Midgard Serpent releases its tail, it will mark the beginning of Ragnarok.

During that cataclysmic event, Thor will fight a final battle with Jörmungandr during which he will slay the mighty serpent only to then fall dead himself from its venom.

According to sea monster myth and legends, the sea bishop or bishop-fish was caught and taken to the King of Poland, who showed it to a group of Catholic bishops. When the bishops released the creature, it made the sign of the cross before disappearing back under the waves.

The bishop-fish is a type of fish that looks like a man—specifically, like a Catholic bishop—while other variations include legends of the sea monk, a fish that looks like a monk. Later experts came to the conclusion that the sea monk was probably actually an angelshark, a type of shark that is also known as a monkfish.

The bishop-fish made an appearance in the fourth volume of Conrad Gesner’s Historiae animalium, an “inventory of renaissance zoology,” as well as Johann Zahn’s Specula physico-mathematico-historica notabilium ac mirabilium sciendorum, and has been associated with the imagery of the half-human, half-fish sages known as Apkallu in ancient Mesopotamian mythology.

This mythical sea monster exists in the world of Avatar: The Last Airbender, but unlike other creatures on this list, this gigantic half-chimera/half-turtle animal is pretty benevolent. In the television series, Aang, the main protagonist, accidentally encounters one of these fearsome creatures when he swims towards a floating island just off the coast in a trance. When he snaps out of it, and realizes the island he’s sitting on top of is the back of this large creature, he dives into the ocean to communicate with it.

The backs of Lion Turtles are so large that they host their own entire ecosystem on their shell. In The Legend of Korra, the successor to Avatar: The Last Airbender, a large number of these creatures existed in the past, serving as both shelter and guardians for humans. In the early days of humanity, settlements were built on the backs of these creatures since they were the only safe place for humans to thrive. This was the case because the world outside the Lion Turtle towns and villages was populated by troublesome spirits that had a tendency to attack humans. In addition to this, Lion Turtles also provided humans with the ability to bend fire, water, earth, or air when they traversed outside the colonies to gather resources.

Avatar: The Last Airbender didn’t create these island-sized Lion Turtles whole cloth, either. They’re inspired by the legends of the Aspidochelone, which are described in medieval bestiaries as turtles or fish so large that they are mistaken for islands by sailors.

Before Godzilla, there was The Beast from 20,000 Fathoms. This 1953 monster movie takes its inspiration from "The Fog Horn," a Ray Bradbury story about a sea monster that falls in love with a lighthouse’s fog horn. In the film, the monster is a Rhedosaurus, a made-up dinosaur that is awakened from hibernation by atomic testing in the Arctic Circle—sounds like a Godzilla movie already, right?

The Rhedosaurus heads south, destroying a lighthouse along the way in a scene reminiscent of Bradbury’s short story, before finally meeting its end at New York’s Coney Island. Brought to life by special effects legend Ray Harryhausen, the Rhedosaurus was far from the last sea monster that Harryhausen would bring to screens—he also contributed creatures to other parts of this list, including the giant octopus in It Came From Beneath the Sea and the Kraken in Clash of the Titans.

In Japan, these sea monsters were pure nightmare fuel for sailors who believed in the myths surrounding this creature. Umibōzu is a giant, shadowy, humanoid-like monster who terrorizes sailors who are unlucky enough to cross paths with it during a voyage. Upon encountering the creature, what was once a beautiful day with calm waters immediately turns into thunderous chaos with harsh waves and never-ending rain. 

According to Japanese mythology, when an Umibōzu appears, they will either immediately attack a ship and drown its crew, or ask for a barrel from the ship’s supply as an offering. If the crew complies with the creature’s demand, sometimes the Umibōzu will spare the ship. But in order to ensure a safe travel away from the sea monster, sailors say that giving the Umibōzu a bottomless barrel will leave the creature confused, giving the ship and its crew an opportunity to flee before the Umibōzu realizes it has been tricked. 

The British author William Hope Hodgson produced a vast and varied body of work around the turn of the century, but what he is perhaps best known for are his stories of horror on the high seas. Returning again and again to the weed-choked wastes of the Sargasso Sea, Hodgson’s sea stories had the ring of truth to them, due in part to the fact that Hodgson himself had served several years as a sailor.

The ocean in a William Hope Hodgson story is populated by all sorts of weird monsters, from ghost pirates to giant crabs to sinister fungi to things even more impossible to describe. Yet describe them Hodgson did, and one example is the eponymous “Thing” in his story “A Tropical Horror.”

“Rising above the bulwarks,” Hodgson writes, “seen plainly in the bright moonlight, is a vast slobbering mouth a fathom across. From the huge dripping lips hang great tentacles. As I look the Thing comes further over the rail. It is rising, rising, higher and higher. There are no eyes visible; only that fearful slobbering mouth set on the tremendous trunk-like neck; which, even as I watch, is curling inboard with the stealthy celerity of an enormous eel.”

More often than not, when we hear the word “Capricorn” our mind jumps to birth charts and zodiac signs—but this sea monster actually has its roots in Greek mythology. Capricorns have the face and upper body of a goat, and the tail of a fish, making it capable of swimming and laying out on shores. Despite anatomically making zero sense whatsoever, these creatures were capable of speech, and were often favored by the gods.

The mythology behind Capricorns starts with Pricus, the original Capricorn who fathered the entire race. Pricus was granted immortality and the ability to turn back time by Chronos, the god of time. When his Capricorn children walked on the shore and stayed out of the sea too long, they ended up becoming regular goats who lost their ability to swim, speak, and think. In an effort to revert this, Pricus used his time-reversing ability to turn the regular goats back into Capricorns. 

Pricus couldn’t keep up with how many times his children repeatedly stayed on the shore, so he gave up trying to remedy the situation, and led a life of loneliness. Taking pity on Pricus, Cronos turned the creature into the constellation we all know today so he can happily see how all of his goat children are doing from the sky. 

This intimidating sea monster has appeared many times throughout the Pokémon series. Gyarados thrives in both fresh and saltwater, and is infamously known for its bad temper and destructive nature. Trainers in the Pokémon universe who are capable of capturing and taming this beast are said to share a powerful bond with Gyarados since the creature will repress its violent instincts to obey its master. 

Gyarados’ sea-serpent design was actually inspired by dragons in Chinese mythology. Unlike European dragons, these creatures are very serpent-like in shape, and have distinct whiskers on their faces. Funny enough, Gyarados also evolves from the very useless Magikarp, a fish Pokémon that is incapable of doing anything but splashing about. According to Pokémon lore, it’s this very dramatic shift in brain structure during evolution that causes Gyarados to have violent tendencies.

Rooted in Slavic mythology, vodyanoy are water spirits who take on the form of a naked old man with a frog-like face. After spending so much time in fresh and saltwater, these creatures tend to have moss, algae, and other plant-like growth all over their bodies, giving them a distinct green color. Vodyanoy are said to be relatively calm, and can often be seen floating down a river or along the shore on a log or driftwood. In popular culture, these creatures have appeared in The Witcher series by Andrzej Sapkowski where they have formed a society, and share the ocean with other races.

Despite their old appearance and peaceful demeanor, if angered, vodyanoy can be quite destructive. In Slavic lore, if anyone angered these sea creatures, the vodyanoy would destroy man-made structures near the body of water it resided in, or drown humans and animals in the area. Worst case scenario, a really mad vodyanoy would drag its victims down to its underwater home where they would be enslaved for eternity. 

Hebrew in origin, this terrifying sea monster is often drawn and described as being a water reptilian of some sort. Immensely large in size, the Leviathan appears in the Old Testament as a sea serpent with multiple heads. In this scene, God kills the creature, and offers its carcass as food for the Hebrews. 

As a creature rooted in a religion that comes from ancient Mesopotamia, this creature has been interpreted in a variety of ways in different religions and cultures. As Judaism continued to develop, the Leviathan upgraded from sea serpent, to the water dragon that many associate with the creature today. In Christianity, the Leviathan is presented as a ravenous demon that has an insatiable appetite for all of God’s creations. In some Christian interpretations, the Leviathan might also just be a giant crocodile. 

Because of this creature’s massive size and underwater dwelling, the name Leviathan is actually used a general term for describing large sea monsters. More than likely due to its very old origins, the Leviathan is pretty much the root of most sea creature myths. Therefore, the Leviathan easily takes home the title for the oldest and most fearsome of sea creatures.

Not all sea monsters are scary, of course. In fact, the star of the Sid and Marty Krofft children’s show Sigmund and the Sea Monsters was a sea monster named Sigmund who got in trouble with his sea monster family precisely because he couldn’t (or wouldn’t) scare humans.

Along with Sigmund himself, the show featured the rest of his aquatic clan, including his two brothers named Slurp and Blurp, and their parents Big Daddy Ooze and Sweet Mama Ooze.

Featured photo: Alchetron