In the open ocean, the murky waters below the ship’s hull seem to rest peacefully in the quiet night. Though there had been many days and nights full of rain and storms, it seemed the waters of the sea had finally calmed. Suddenly, there is a cry from a shipmate at the front of the craft. The calm waters begin bubbling up with the vengeance of the sea. As crew mates around you start rushing to ready the sails in an attempt to stop whatever threatens to come up from the depths of the ocean, you stand and wait for your fate to catch up to you. There is no point in running – a sea monster will soon be upon you.

What is a Sea Monster?

A sea monster is, by definition, any creature that comes from the sea – real or mythical – and is unusually large or threatening. There are hundreds of accounts of these creatures – any culture that had contact with the sea has at least one form of sea monster reported in their mythological history. Interestingly enough, however, there do seem to be some accounts of ‘friendly sea monsters.’

Sea Monster

What Inspires the Sea Monster Stories?

There are many speculations as to what could have possibly inspired the myths of the terrible sea creatures and monsters that have become infamous in mythology worldwide.

Misidentification of Sea Creatures

It is thought that some of these stories could have been caused by actual sea species that were both new and terrifying to the sailors and explorers who were just beginning to venture across the ocean. It is also thought that some of the mythological creatures that have been reported are possibly just carcasses of sharks and whales that decomposed in a manner that made them look significantly larger and scarier.

Recent studies have shown that sperm whales and basking sharks decompose in such a way that can make them seem otherworldly. The sperm whales decompose in a manner that causes the blubber to detach from the rest of the carcass. At times, it can grow a hairy texture on the whitish blubbery mass that would certainly seem foreign.

The basking shark undergoes a similar decomposition process which causes them to lose their lower head and fins while being recycled. The end result is fairly similar to the appearance of a plesiosaur. This strange appearance could have certainly been the cause of many horrific tales of monsters at sea.

Possible Cryptids

There are also those who wonder if the answer may be more promising. The majority of the world’s oceans are still largely unexplored. This makes it possible for these creatures from myths to be cryptids – not just myth. There are many pseudoscientists who are hopeful that we will discover these strange creatures when diving technology improves.

Some also speculate that the strange appearance of the reported creatures could be linked to the early sea dinosaurs. It is possible that the sea monster cryptids are descendants of early dinosaurs and other megafauna.

Missing Persons

It is possible that the myths surrounding these creatures could have also been created by the concern for missing persons that disappeared during storms (hurricanes, typhoons, flooding, etc.) or sailors that never came back home. It was likely easier to imagine that a creature of some sort was responsible for their disappearance – especially since many sea monster stories leave room for the victims to be alive and well somewhere. Tales like that of the Finfolk and the Vodyanoy speak of creatures who would kidnap humans and force them to marry their kind. These stories also told that part of this kidnapping required to remain under the surface of the sea for the rest of their lives. In spite of this, there was often hope that the victims would be able to escape and come back home.

Seemingly Unexplainable Ship Damage

Another possible explanation is simply that the creatures were invented to explain ships that were destroyed by hurricanes and other tropical storms. The remains of a shipwreck would have seemed nearly impossible to comprehend for many early cultures. It is plausible that many sea monsters were created in order to explain how these ships became so distorted and torn apart.

Inanimate Floating Objects

All other explanations typically fall under a category of mistaken identity of inanimate objects. This could be random floating objects like driftwood, ship wrecks, and rafts. However, it can also be plant based life such as floating kelp that is to blame for the mistaken identity.

Famous Sea Monsters

Regardless of what causes the sea monster myths, it can be agreed that there are some monsters that are as terrifying in modern day as they were the day they were created. There are also stories of sea monsters that are not as popular on a global scale, but have significant meaning in their respective region of origin.



In Greek mythology, it is common for a sea monster to be referred to as Cetus. This term is fairly vague. Based on context clues, however, it seems likely that Cetus was some sort of serpent/dragon, shark, whale, or fish. The most famous instance of Cetus being used is when Poseidon sent Cetus to devour Andromeda. This was done to punish Andromeda’s mother for making a boast that her daughter was more beautiful than all of the nereids (other creatures of the sea – one of which was Poseidon’s wife). Andromeda was saved at the last minute by Perseus, but it is noted that he was only able to overcome Cetus by using Medusa’s head.


There was also a Greek monster called Charybdis who terrorized sailors and warriors when they tried to pass through the Strait of Messina. It is said that Charybdis lived under a small rock on one side of the Messina channel. She is thought to have been the daughter of Poseidon and Gaia who was turned into a terrible monster by Zeus. Part of his curse was to make her thirst for the sea so much that she had to swallow large quantities of water 3 times each day. This process indirectly caused whirlpools that is estimated to have been nearly 75 feet across. She was chained underneath a rock on the Strait that made it impossible to move from her location.

There are also versions of this story that simply claim that Charybdis was the name of the whirlpool in the straits. This version is supported by the fact that there is a whirlpool in the same location. This whirlpool, however, can only affect small ships in extreme weather conditions – not the mighty Greek ships of that day and age.

The Cirein Croin

In Scotland, a terrifying creature known as the Cirein Croin loved to terrify its victims before consuming them in one bite. The creature has a typical water dragon or serpent shape that is vicious and terrifying, but it uses its ability to shape shift to turn into a seemingly harmless fish. When in this form, it is no bigger than the palm of a human hand.

When fishermen caught the Cirein Croin in its small fish form, it would suddenly transform back into its original terrifying state and swallow the fisherman whole.


Finfolk are known in Celtic mythology as a terrible group of mermaid-like sorcerers. These beings alternate their time between an underwater paradise and a colony on dry land. They were often known to take advantage of human populations and take the most desirable men and women with them to be their spouses. These people were never seen from again, though it is thought that they led long lives.


Grindylows are water demons that appear to us from British folklore. They are supposedly most common in the county of Yorkshire. Grindylows were water demons that liked to wait in cold water for a victim to happen by – usually a child.

When a child ventured into cold water, the Grindylow would pull them into the water with long fingers and drown them. It is thought that the Grindylow was invented to keep children from wandering off into dangerous waters.


Living off the coast of Cameroon, the Jengu is an example of a sea monster who seems to mean well. They are thought to be very beautiful mermaids with extremely curly hair and a gap-toothed smile. They live in both the rivers and the seas and are known be able to cure illness and bring good luck to their worshipers. Some people even believe the Jengu are able to communicate with the spirit world and relay messages back to humans.



Another famous sea serpent is the Midgard Serpent who was named Jormungandr. This creature was a child of giants (Loki was his father) and was therefore an enemy of the gods. There were many fearful things associated with the Midgard serpent, but perhaps the most terrifying was the prospect of Ragnarok. This was thought to only be held off by the fact that Jormungandr had wrapped himself around Midgard and held his own tail in his mouth. It is thought that this action is what holds the world together – when Jormungandr lets go, it will signify the beginning of the end times.

The Kappa

The Kappa is a water imp that was known to inhabit bodies of water in Japan. This terrible creature was known to have a humanoid body, with superhuman strength and terrifying speed. They were known to wait by the edges of water (and sometimes in bathroom toilets) for victims to come by. At this time, they would pull their victims into the water and drown them in order to steal their shiri (a person’s life force). Women were sometimes able to survive a kappa attack, but they would often be sexually assulted by the beasts because the Kappa gained sexual pleasure from being able to touch the shiri.

It was thought that the only way to survive a Kappa attack was to take advantage of their oddly polite behavior and incredible honesty. If one saw a Kappa, they should bow out of respect. The Kappa would do the same (because it was obsessed with politeness) and would spill the water out of the cup in its head. This water was the source of all a Kappa’s power – without it. The creature was powerless and may even die. A person was then free to go, or could choose to refill its water in exchange for a promise that it and its kin would never bother the city of that person again. If the Kappa agreed to this promise it wouldn’t be able to break it and the person and their family would be safe from future attacks.

The Kraken

The Kraken is an infamous sea monster who was known to terrorize sailors off the coast of Norway. This enormous beast was thought to release a substance made up of its previous meals (similar to chum) into the water when it wanted to feed. This would cause an impressive amount of fish to flock to the area in order to feed on the bait. When enough fish had gathered , the Kraken would reach up and swallow them all, then fall into a deep sleep while it digested the food.

When sailors first realized that fish were drawn to a particular area at certain times when the Kraken was feeding, they would attempt to sail overhead and drop their nets to skim off of the Kraken’s food source. This greatly upset the Kraken, causing it to sink the ships and eat the sailors. Whenever a ship tried to steal food from the beast – or bothered it in general – the Kraken would create a terrible whirlpool and raise its tentacles out of the water to capsize the vessel in question.

It is sometimes hypothesized that the tale of the Kraken was inspired by sightings of giant squid. This is partially because of the description of the anatomy of these creatures, and partially because giant squid are known to use similar hunting methods.


One of the most famous sea monsters was brought to the forefront by Christianity. This monster is Leviathan – one of the first creatures to be created by Yahweh. Leviathan started out as a gentle creature that was content to roam the seas with its partner. Soon, however, it was corrupted and became a creature that loved to cause chaos and destruction. In order to save the world, Yahweh was forced to destroy the female Leviathan so that they could not reproduce. The male Leviathan was left for the time to roam the oceans and cause mayhem. He was known to have many dragon-like abilities and to be impossible to kill. This combination made him the most feared monster in history. He was known to delight in causing the water around him to boil at intense temperatures – causing the skin of sailors to melt slowly and painfully. It was thought that to see Leviathan was to be fated for death. There are no reports of Leviathan being spotted by someone who survived to tell the tale.

Mami Wata

Mami Wata is known to be a water deity that can be found off the coasts of West, Central, and Southern Africa. She is also thought to exist in the waters of island countries with large African diaspora populations.

Mami Wata
Mami Wata

Mami Wata is known to be a beautiful woman with curly or kinky hair that is combed straight back. She is often seen as being a mermaid creature with either a fish or serpent tail, but she is also capable of showing herself in human form.

Mami Wata is known to prefer one on one interactions with her followers and often abducts believers while they are swimming, boating, or looking for sexual favors. She takes them to her realm and often teaches them secrets or gives them riches that allow them to return as rich, more attractive, and more content than when they left.

Sometimes Mami Wata asks for a man to give her his sexual faithfulness and promise her secrecy for the acts they have indulged in together. If he agrees, she showers him with great riches and fortune. If he breaks the promise, however, he will be in ruin and likely lose his job, family, and money.


Scylla was once a beautiful naiad who was chased after by many suitors. One day, Poseidon caught sight of her and decided to claim her for his own. Unfortunately, this caused Amphitrite to become very jealous. Amphitrite decided to poison the water of the spring where Scylla loved to bathe, turning her into a terrible monster.

There are several different renditions of what Scylla was turned into. Some of these renditions say she remained a beautiful maiden from the waist up, but had a terrible serpent’s tail and six dogs heads around her waist that hungrily sought out men to devour as part of her revenge. Other accounts say she was made to be a fearsome monster above the waist as well. She is depicted as having 4 eyes and 6 additional necks – each with a terrible dog’s head that had three rows of shark teeth in their mouths. She is also sometimes said to have 12 tentacle legs and a cat’s tail.

She was truly terrifying to crews attempting to pass through the Strait of Messina. She lived directly across from a whirlpool monster named Charybdis and sailors would have to choose which monster they wanted to take their chances with. Though many chose to pass on her side of the strait, they had to sacrifice 6 men to her hungry mouths to do so.


Although beautiful in appearance, sirens are some of the most feared sea monsters because of their mischievous nature. There were two forms of sirens. The first was a woman with the arms and legs of a bird and a beautiful human face. The second was a woman with a fish tail that was also very beautiful. These creatures were known to swim or fly by ships that had been at sea for a considerable amount of time. They preyed on men’s need for companionship and the considerable time they had spent without a woman’s touch. The sirens would sing songs that were so beautiful, men would decide to climb out of the ship and jump into the water to be with the lovely maiden. When they reached the water, however, a terrible surprise awaited them. The sirens would drag them off to a remote place or the depths of the sea and feast on their flesh.


Perhaps the most terrifying sea monster in Japanese mythology is the terrible Umibozu. Though many monsters appeared when the seas were stormy or other dangerous conditions were present, Umibozu preferred to take his victims when they least expected it.

When sailing along a calm sea on a day with good weather, Umibozu would suddenly cause a storm to come out of nowhere and create waves that rocked ships and terrified the passengers. Then, he would rise from the sea – a black humanoid figure with hollow eyes and an erie smile. Should anyone speak to the monster or offend it in any way, the Umibozu would capsize the ship and claim the souls of the sailors.

There was, however, thought to be an out. If the Umibozu was offended by a human, it would ask for a barrel. Then it would use this barrel to fill the boat with enough water to drown it and kill all sailors aboard. However, if a smart crew was able to give the Umibozu a bottomless barrel, it wouldn’t be able to scoop up any sea water and the crew would at least have a chance to escape back to shore.


Emerging from Slavic mythology, the Vodyanoy was known to be a disgusting creature that supposedly embodied the spirit of an unbaptized man. This creature enjoyed taking the form of an irresistibly attractive man and luring women into the water where it would drown them. The Vodyanoy didn’t always have murderous intentions though – sometimes it kidnapped young women and forced them to be its bride. Either fate was terrible, but it was sometimes thought that living the rest of one’s life out with such a monster was a fate worse than death.

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