American Oceans

Sea Monsters

70% of the world’s surface is covered by water, and throughout history, humans have been preoccupied with wondering what lies below the storm-tossed seas. These adventures have come with horror stories of sea monsters – but are the creatures real or mythical? 

giant sea monster

These creatures are typically large and threatening, and each society that came in contact with seas or oceans has some kind of sea monster in its history.

Keep reading to learn more about the spookiest sea monsters that have tormented human imagination for centuries.

History of Sea Monster Myths

The myths of sea monsters and animals that live deep beneath the water are nearly as ancient as time. Stories about these monsters were frequently inspired by encounters with unusual and strange real-life species, such as the enormous squid, whales, and seals, and optical illusions like inanimate floating objects.

Another inspiration for sea monster monsters is unexplainable ship damage. Remains of shipwrecks from hurricanes and other sea storms were inexplicable to humans. So there’s a possibility that the creatures were developed to explain the distortion of ships.

The proportions of these animals were often exaggerated since there is no reference point for size in the open sea. Nevertheless, it’s intriguing to note that these mythical sea creatures exist in many civilizations and have similar names and origins.


sea monsters

The legendary Kraken is an iconic sea monster that was believed to be a menace to sailors on the Norwegian and Greenland coasts.

The name of this monster derives from Norwegian, which means “unhealthy or twisted beast.” It could be the colossal sea monster ever envisioned. According to some accounts, it was more than 2.5 km in circumference and had arms the size of ship masts.

It was thought that this mythical sea monster spewed a substance of its last meal into the sea when it needed to feed. The chum would then attract a shoal of fish into the area to dine on the bait. Once enough fish accumulated on the bait area, the Kraken would reach up and swallow all the fish before submerging back into deep waters to sleep and digest the food.

The hypothesis behind the existence of the Kraken myth is based on the sighting of a giant squid. This suggestion comes from the anatomy of the giant squid and its similar hunting methods. The mythical Kraken has been featured in various top-rated movies, tv shows, and films.


an image of the mythical kraken sea monster

Greek mythology is rich in gods and monsters, so it’s unsurprising there are some notable Greek mythical sea monsters.

Cetus is a common name for sea creatures in Greek mythology, making the word vague. But contextually, Cetus is the Greek version of the mythical Kraken. The Greeks often pictured Cetus as a hybrid beast. It had forefeet, enormous jaws, and a scaly body like a giant sea snake

Cetus ravaged Aethiopia’s coast until the frantic leader, King Cepheus, sought advice from an oracle. This sea monster was Poseidon’s flunkey sent to eat Andromeda in retaliation for her mother’s bragging that Andromeda is the most beautiful of all other sea creatures.

Perseus came to the rescue of Andromeda at the last minute by holding Medusa’s head up, which turned Cetus into stone. The Cetus was put among the stars to symbolize Perseus’ valor and warn the Greek people against anger or envy.


a drawing of the leviathan sea monster

This terrifying sea monster boasts Hebrew origin, featured in the Old Testament of the Bible, which makes it the oldest sea creature.

The Leviathan is depicted as a sea reptile – a massive primordial sea serpent with multiple heads. In the biblical context, God slays the monster and provides its remains as food to Hebrews in the wilderness.

However, the Leviathan has been interpreted in divergent ways by various societies and religions. As Judaism progressed, the Leviathan evolved from a spooky sea serpent to a sea dragon, which resonates better with people today. Modern Christianity portrays the Leviathan as a hungry monster with an insatiable appetite for God’s creatures.


illustration of the mythical Jörmungandr

From Norse mythology, Jörmungandr is a son of Loki and Angrboda, a terrifying sea creature known as the Midgard or World Serpent.

It is perceived that the serpent is long enough to wrap itself around the earth and bite its tail.

But that’s not the horrid thing about this sea monster – according to the myth, it will be the beginning of the end of gods if Jörmungandr lets go of his tail, an aspect called Ragnarök or apocalypse.

The sea serpent is depicted as a pivotal villain in Norse mythology and an enemy of Thor, the God of thunder. It is said that the two will go to war in the event of Ragnarök.


illustration of Scylla sea monster myth

Scylla is a terrifying sea monster from Greek mythology. She was said once to have been a beautiful nymph who several suitors pursued.

The race to win Scylla’s heart made Amphitrite envious after Poseidon saw her and wanted to take her for himself. As a result, Amphitrite plotted to poison the stream water where Scylla bathed, which turned her into a terrifying monster.

Various accounts explain what Scylla transformed into after bathing in the poisoned water. Some claim that she retained her stunning beauty from the waist up, but she developed six dog heads around the waist and a dreadful serpent tail from the waist down. 

In other renditions, Scylla also had terrible features above the waist, including six necks – each with a monstrous dog head, four eyes, and three rows of shark teeth. From the waist down, she’s depicted to have a cat’s tail and a dozen tentacle legs.


The Lusca is a scary sea monster believed to inhabit the Caribbean waters, especially around the Bahamas. The frightening creature is said to look like a giant octopus with gigantic tentacles. Other folklore claims that Lusca is an octopus-shark chimera, while others depict the beast as having dragon-life features but with tentacles.

This sea monster is said to be massive, growing over 75 feet in length, and some theories claim that the Lusca can change its body color. Lusca is typically associated with the blue holes of the Bahamas coast, with various sightings reported at the island of Andros, which boasts up to 50 ocean blue holes.

Various mystical disappearances, deaths, and sinking ships in these deep holes have been attributed to Lusca. But most locals think it is folklore to keep them away from the blue pits.


Umibozu a japanese sea monster

From Japanese mythology, Umibōzu is arguably the most horrid sea creature in Japan’s Yokai-laden waters. This sea spirit, which is more of a paranormal phenomenon than a creature, has been reported many times by Japanese sailors.

It manifests when the water is calm and rapidly churns and stirs the seas, shattering ships and sending sailors scrambling for safety. According to folklore, the only method for escaping the monster is to offer it a bottomless barrel and sail away to the shore while the creature tries to comprehend the thing and becomes confused.

Umibozu accounts vary greatly. They may take the form of anything, ranging from a hairy beast like a sperm whale to a lovely lady capable of transforming into a terrible monster. 

The traditional Umibozu account is most commonly depicted by ukiyo-e painters – that of a big black head with two large eyes springing out from the sea waters. However, most experts believe that Umibozu is a misinterpretation of natural occurrences such as rogue waves and sea storms.


the Hafgufa mythical monster

The Hafgufa is a legendary monstrous sea creature from Norse mythology that inhabited the black depths of the Greenland Sea. The monster was so enormous that it could be mistaken for an island when it remained stationary. It’s said that Hafgufa was hardly ever seen, but whenever it appeared, it was always spotted in the exact two locations.

The Hafgufa was regarded as the mother of all sea monsters and could devour anything it could capture in the sea, from sailors and fish to even ships.

The only physical feature of the Hafgufa sighted was its nose which would emerge out of the seawater at night when the tides were low. This terrifying creature’s nose could be mistaken for two huge rocks; if sailors could mistake it for a land mass, they would become the monster’s snack.

Devil Whale

the devil whale from mythology

The Devil Whale is a mythological sea creature that resembles a massive demonic whale. In this legend, this whale is gigantic and can devour an entire ship. The devil whale is believed to have its body at the ocean’s water surface when asleep, gathering sand until it looks like a desert island.

The sight of the devil whale in the water allures seamen to land with the misguided notion that they are docking on dry land. As a result, they become comfortable and settle on the island. However, upon lighting fire, they would irritate the devil whale, submerging it into the water to cool its skin and sinking the sailors and all their belongings into the sea waters. 


Iku-Turso is a scary sea creature from Finnish mythology. The monster’s name translates to “the eternal Turso” and was often associated with war and disease in the Finnish myths. Iku-Turso is a jerk of pure evil in the form of a terrifying sea creature that resembles a giant bearded octopus with giant tentacles and suckers.

It is said that when the Iku-Turso was agitated, he would grow massive dragon-like wings that were sensible for billows and relentless waves in the sea. The creature is believed to have stayed solitary in the deep-sea waters of Pohjola. 

However, when provoked, Iku-Turso possessed a fiery and frightening temper and would attack anybody in sight viciously by shooting arrows that caused disease.


From Japanese mythology, the Akugyo is a frightening monstrous fish that is believed to inhabit the Japanese waters near Kibi Province. The mermaid-like monster is said to have a giant human-like head with two white horns and human arms, with the rest of the body resembling fish, covered in gold and silver scales.

The sighting of this evil fish is rare, with the latest recorded case dating back to 1805 when an Akugyo was sighted off the coast of Echigo Province. This scary sea creature measured a whooping 11 m in body length, and the horns measured over 60 cm long.

It is said that boats would get stuck on the backs of these creatures that would then capsize the ship and devour the sailors.

In addition, a legend is told of Izutsuya Kanroku, a taiko master from Kaga whose boat got stuck on the back of the Akugyo when sailing in the Sea of Japan. Left with no option, he played his taiko drum with all his strength such that its sound shook his boat loose, and he could scatter for safety and save his life.


Charybdis sea monster illustration

Greek mythology is indispensable in the tales of terrifying sea monsters, and Charybdis is another such powerful and dangerous creature. Moreover, she was not merely a monstrous sea creature; she was also a natural force that often emerged in Greek mythology as a hurdle in various Greek heroes’ quests.

Charybdis was believed to dwell beneath a rock along the Messina, terrorizing sailors as they attempted to cross the Strait of Messina. According to the mythos, she was a human daughter to Poseidon and Gaia, who was turned into a dreadful monster through Zeus’ curse.

Part of the curse entailed Charybdis needing to quench her thirst with vast volumes of water three times a day. This process resulted in the formation of giant whirlpools in the strait that are believed to measure 75 ft. in diameter. The presence of a whirlpool at the same spot lends credence to this tale.


Akkorokamui sea monter illustration
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The gigantic Akkorokamui is said to be a scary blend of an octopus and a female human that dwelled in Uchiura bay in Hokkaido, Japan. It is believed to have a vivid red hue, and with its enormous size that can stretch up to 120m in length, its color would reflect in the sky, turning it red.

The Akkorokamui was reported to have the ability to self-amputate and regenerate tentacles. This attribute reflects the belief that Akkorokamui possesses healing qualities in Shinto. As a result, adherents believe offerings to Akkorokamui may cure physical diseases, particularly fractured limbs and disfigurements.

This monster is said to have been so big that it could swallow a whole whale and ship in a single gulp. Any ship that was unreasonable enough to sail close to the Akkorokamui was to be consumed, including the sailors. As a result, locals have avoided water whenever the sea and sky turn red.


Cirein-Cròin was a sea monster lurking off the coast of Scotland in Gaelic folklore. Based on its description in old tales, it’s a sea serpent or snake-like creature ferocious and big enough to devour up to seven whales in one meal.

This sea creature was believed to conceal its monstrous nature by transforming into a small fish when it crossed paths with fishermen. But when the fishermen captured the Cirein-Cròin in its little form, it unexpectedly shifted back to its frightening monstrous form and devoured the fisherman and all sailors in the boat.

The myth depicts Cirein-Cròin as a ruthless monster that enjoyed tormenting its prey first before swallowing it in one bite.


native american mythical monster Apotamkin
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Apotamkin is a native-American mythology sea creature frequently misinterpreted as a vampire, most notably in the popular film series “Twilight.”

In the Passamaquoddy mythology, the Apotamkin is believed to be a colossal sea monster with long hair and long sharp fangs that inhabited the waters between the Passamaquoddy Bay of the US and the New Brunswick province of Canada.

The most crucial element of the Apotamkin myth is that it conveys a vital lesson to children and warns them against exploring hazardous water bodies on their own. Apotamkin, according to the Passamaquoddy culture, is a benevolent sea creature that saves children from breaking through weak ice and other water tragedies.

Stoor Worm

mythical Stoor Worm monster
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The stoor worm is a gigantic sea dragon in Orcadian mythology that could infect vegetation and murder animals and people with its vile breath.

According to legend, the king of one country was terrified by the beast’s advent and instructed to provide it with a weekly offering of seven virgins. In despair, the king released a proclamation promising his daughter’s hand in marriage and a magical sword to anybody who could defeat the monster. 

The beast was slain by Assipattle, a local farmer’s youngest son, by slicing open the monster’s liver and shoving in a smoldering peat. He blew the peat until it lit, burning the Stoor Worm. Upon dying, the Stoor Worm’s teeth fell out and became the islands of the Faroes, Orkney, and Shetland, while its carcass became Iceland.


Lyngbakr is a Norse mythological sea monster recorded in the Örvar-Odds saga that was said to have lurked in the seas near the coasts of Greenland and Helluland.

As the legend goes, the giant whale-like creature feigned to be a heather-covered island to attract sailors. Once the sailors landed on the island, the monstrous sea creature sunk into the abyss, dragging the whole crew with it.

In the saga, Örvar-Oddr and his men were cruising southwesterly across the Greenland Sea in revenge against the troll Ögmundr Floki, who had killed Eythjof. They saw two rocks rising out of the sea as they sailed and later went past a vast heather-covered island. 

Örvar-Oddr, intrigued, decided to turn back and send five men to investigate the island, but when they approached the island’s previous location, they observed that the island and the two rocks had disappeared. Had they docked on the island, they would have vanished with it. 


Morgawr is a gruesome giant sea monster that is believed to have inhabited Falmouth Bay and the Helford River, an area that was later called the “Morgwar Mile.”

This massive and well-known sea monster is known for having two to three big humps on its back and a long, scaled neck that resembles a gigantic snake. The Morgawr is also said to have short, spiky horns over its eyes and many spikes along its long, terrifying neck.

Since its discovery in 1906, various sightings have been reported. Several theories about the identification of the Morgawr have been developed, including a hoax or mistaken identity and the possibility that the sea serpent is the last of the dying species of Plesiosaur or an unknown species of long-necked seal.


mythical sea turtle with an island on its shell

The Aspidochelone is a marine monster depicted as a giant whale or enormous sea turtle in the Physiologus, a didactic Christian literature from the 2nd century AD authored in Greek by an anonymous writer.

This sea monster gave onlookers the impression of a massive creature with enormous spines along the ridge of its back, portraying the features of various breeds of the sea turtle

However, some of the earliest literature claims that when the Aspidochelone was hungry, it would open its mouth and release a delicious aroma to lure fish. According to this account, the monster was most likely a whale, not a turtle.

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