Sea Serpent
Binomen Cadborosaurus willsi
Halsydrus pontoppidani
Megophias monstrosus
Pelamis megophias
Scoliophis atlanticus
Body type Serpentine
Average length Varies (typically 10 to 30 meters, although some can be 60 meters or longer)
Sentience Sentient
Sapience Non-Sapient (usually)
Aggressivity Varies (typically low)
Place of origin Worldwide waters
Habitat Oceans
Diet Carnivorous
Locomotion Swimming
Related species Dragon
Status DD
Behind the Scenes
Universe Real

Spotted by sailors from all places and eras, Sea Serpents figure among the most widely reported cryptids and legendary beings. Their size and appearance are enormously variable, and their true nature is hard to guess, since they may possess features indicating reptilian, mammalian, piscine, or invertebrate affinities, depending on each report. Many cryptozoologists believe that the term "Sea Serpent" actually denotes an artificial category for numerous related and unrelated species - with the only features shared by all of them being their huge size and elongated serpentine body.

Despite the widespread use of the term "Sea Serpent", freshwater varieties are just as common. These may be referred to as "Lake Serpents" or "River Serpents", but are more commonly lumped together in the vague denomination of "Lake Monster", which also includes beings with non-serpentine body types, such as crocodilian, plesiosaurine, or chelonian. In Bernard Heuvelmans' traditional classification which defines nine types of "Sea Serpents", some of the types are likewise not serpentine at all, particularly the long-necked seals, as well as the giant crocodiles and turtles.

Traditionally, Sea Serpents in myth have often been associated with Dragons, and sometimes with Mermaids or Nāgas. The fact that the word "dragon" in many languages was historically interchangeable with "serpent" certainly doesn't help. Asian dragons in particular, with their very serpentine bodies, are often associated with the sea. In some cultures, a few individual Sea Serpents may be regarded as deities and are often an important part of mythology, with the vast Jörmungandr - the "Midgard Serpent" - being probably the utmost example.



The fact that so many Sea Serpents are found in extremely cold waters probably indicates that they possess some form of temperature regulation, being either homeothermic or gigantothermic.

Furthermore, they're almost invariably described as swimming in a vertical undulating fashion, which is a feature strongly associated with swimming mammals and completely unheard-of in swimming reptiles and fish. The swimming pattern therefore creates a very strong argument for the Serpents being mammalian creatures, rather than reptilian. Additionally, many of them have been described with hair, manes and/or whiskers. Conversely, some Sea Serpents have been described as looking more reptilian or piscine, or rather with crustacean features such as chelae, or even mollusk features such as tentacles.

Heuvelmans' ClassificationEdit

In his 1965 study, Le Grand-Serpent-de-Mer, le problème zoologique et sa solution, Bernard Heuvelmans ascribes a scientific binomen to five proposed species of oceanic mammals.

  • "Long Cou" / "Long-Necked" (Megalotaria longicollis): Long-necked giant sea-lion; reported worldwide.
  • "Super-Loutre" / Super Otter" (Hyperhydra egedei): Long-necked otter-like archaeocete; once reported in the northern seas, but believed to be extinct.
  • "Multi-Bosses" / "Multi-Humped" (Plurigibbosus novae-angliae): Archaeocete with a series of humps on its back; reported in the North Atlantic.
  • "Cheval Marin" / "Merhorse" (Halshippus olai-magni): Pinniped with a head resembling that of a horse but with prominent whiskers; reported worldwide.
  • "Multi-Ailerons" / "Multi-Finned" (Cetioscolopendra aelieni): Archaeocete with a body covered in armored plates and with lateral projections resembling fins, giving the impression of a crustacean or centipede-like animal; reported worldwide. Nowadays this species is most commonly known as the Con Rit. It should be noted that although Heuvelmans believed it to be a mammal, other researchers like Karl Shuker have proposed an invertebrate such as a giant isopod or undiscovered oceanic centipede as more likely candidates.

Additionally to the above, Heuvelmans also describes four non-mammalian types of sea monsters, for which he gives no binomen. These are the "Yellow Belly", a creature with uncertain affinities; the "Marine Saurian", which is a giant crocodile; the "Father of All Turtles", which is a giant sea turtle; and the "Giant Eels", which can be further divided in those which are actual eels and those which are more akin to giant serpentine sharks (perhaps related to Chlamydoselachus anguineus, the frilled shark).



It is traditionally believed that the Trojan priest Laocoön and his sons were strangled to death by sea serpents sent by either Athena or Poseidon after trying to expose the Trojan Horse as a trap by the Greeks. These serpents are usually represented as larger than most snakes, but still very far from gigantic - which makes sense as a truly enormous serpent would hardly be capable of strangling someone, and would most likely either eat them or crush them instead.

In the folklore of the Orkney Islands figures the primordial monstrosity known as the Stoor Worm, a Sea Serpent so huge that it could easily flood Europe just by emerging from the waters. To keep that from happening, the people were forced to sacrifice victims to keep the monster appeased. When a local sorcerer warns the king that his daughter shall be the next victim, the king offers his own kingdom to anyone who can slay the giant monster. The humble villager Assipattle manages to kill it by throwing burning peat down the creature's throat. As the monster dies, its teeth fall off and become the Orkney, Shetland and Faroe Islands, while its curled, still-burning body ends up becoming the volcanic Iceland.

Meanwhile, Japanese folklore also includes a story of a Sea Serpent demanding sacrifices. Described as an evil god, the dragon-like Yofune-Nushi lived in the seas surrounding the Oki Islands and was about 26 ft. in length, with scaly skin and small legs, but nevertheless snake-like in its overall shape. Every year the monster demanded a virgin girl to be sacrificed, until one year in which it was slain by the brave young maid named Tokoyo.


It is a well-known fact, that during the Punic war, at the river Bagradas, a serpent one hundred and twenty feet long was captured by the Roman army under Regulus, after they besieged it like a fortress, using ballistae and other engines of war. Its skin and jaws were preserved in a temple at Rome until the time of the Numantine war.
— Pliny the Elder, Natural History

Aristotle, in his Historia Animalium, described sea-serpents that resembled their land-based counterparts, were apparently normal-sized and inhabited shallow waters. However, he did also talk about giant sea serpents in Lybia, which were known to prey upon oxen.

Another famous story involves St. Olaf's feat of killing a humongous Sea Serpent and tossing its body on a cliff side - the mark of the beast's silhouette being still visible today.

In the 16th century, famous historian and cartographer Olaus Magnus described the Sea Serpent as a fearsome and enormous predator of the Norwegian seas which - although it did feed on sea animals - would also venture onto land to prey upon sheep, pigs and cattle. It also attacked ships to devour sailors. The size of the animal was given as 200 ft. in length, 20 ft. in width, and it was described with long hair on its neck, but also "black scales and flaming red eyes".

In 1752, Erik Pontoppidan published his The Natural History of Norway, which included eyewitness accounts from highly credible individuals who documented their encounters with Sea Serpents and other marine cryptids such as Mermaids and the Kraken.

Perhaps the earliest Sea Serpent to be given a scientific binomial nomenclature was the so-called "Stronsay Beast", a mysterious 16-meters-long carcass which washed ashore the island of Stronsay, Scotland in 1808. The creature had a serpentine body and three pairs of short paws or fins. Its back was covered in bristles which would glow in the dark when wet. The fact that its skeleton was cartilaginous strongly suggests selachian affinities. Anatomist John Barclay named the new species Halsydrus pontoppidani in honor of Pontoppidan.


Another famous case occurred in Gloucester, Massachusetts, in 1817, with the 50 ft. creature being once again described as a new species, tentatively named Scoliophis atlantica. Just a few years later, in 1819, the famous polymath Constantine Samuel Rafinesque-Schmaltz published his Dissertation on Water-Snakes, Sea Snakes, and Sea Serpents, describing 100 ft. monstrosities alongside real, regular-sized sea snakes, and proposing two possible names for it: Pelamis megophias if it turns out to be closely related to the snakes of the Pelamis genus (nowadays known as Hydrophis); and Megophias monstrosus if it turns out otherwise.

In 1892, Anthonie Cornelis Oudemans published The Great Sea-Serpent, but the species that he described (Megophias megophias) wasn't actually serpentine, but rather a gigantic pinniped with an extremely long neck and tail, somewhat reminiscent of Heuvelmans' long-necked seals. Oudemans explicitly denied the earlier idea by Rafinesque-Schmaltz that the beast was an actual serpent, claiming that for each report describing it as reptilian there are twenty others describing it with smooth skin more reminiscent of a mammal.

In 1905 a curious Sea Serpent was sighted by the crew of the Valhalla off the coast of Brazil. This case was notable for the fact that two renowned naturalists were among the witnesses: Michael J. Nicoll and E. G. B. Meade-Waldo described an elongated mammalian animal with a large dorsal fin and a turtle-like head.

In 1937, a Sea Serpent carcass was retrieved from the stomach of a sperm whale in Vancouver. Nicknamed Cadborosaurus willsi by the locals, its appearance perfectly matched that of a species which had already been reported in the area before, described as a camel-headed carnivorous serpent. The creature is also attested in the mythology of the native peoples of Canada and Alaska, where the Manhousat people know it by the name hiyitl'iik. There have been numerous sightings of live Cadborosauruses in the North Pacific throughout the 20th century.

Possible relationsEdit


Some scientifically-recognized oceanic species with a serpentine appearance, which may or may not be related to the Sea Serpent phenomenon include: frilled sharks, eels, oarfish and actual sea snakes. Some giant oarfish (Regalecus glesne) have been reported to grow up to 17 meters (56 ft.), which makes them certainly qualify as a veritable "Sea Serpent" of sorts.

Although truly gigantic eel species have never been officially recognized by science, it's highly likely that they exist. In 1930 the famous Dana expedition led by oceanographer Johannes Schmidt caught specimens of eel larvae of truly gigantic proportions in the Cape of Good Hope. The largest of the larvae measured circa 1.8 meters in length. Based on the larva to adult growth rate of known eel species, Bernard Heuvelmans suggested that an adult member of this species would be about 30 meters long. It was not until 1959 that another specimen of these "Super Eel" larvae was found, this time off the coast of New Zealand. This one was nearly a meter long and received the scientific name of Leptocephalus giganteus. Unfortunately, however, it was found that these belonged to a distinct family of eels in which the growth rate from larval form to adult form isn't as impressive, rendering Heuvelmans' predictions more doubtful.

Alternatively, Sea Serpents have been speculated to represent modern descendants of prehistoric lineages such as plesiosaurs (long-necked reptiles), mosasaurs (giant sea lizards, actually related to snakes) or zeuglodons (elongated cetaceans). It should be noted that of all these animals, only zeuglodons would be expected to swim in the vertically-undulating fashion that is typically reported in Sea Serpents. All fish and reptiles swim in a laterally-undulating fashion, with the vertical undulation being very characteristic of mammals, and consistent with an archaeocete identity proposed by Heuvelmans for the "Many-Humped", "Many-Finned" and "Super Otter" types. It's also consistent with the pinniped identity proposed by Oudemans, and by Heuvelmans for the "Long-Necked" and "Merhorse" types.

Another possibility, defended by modern authors such as Oberon Zell-Ravenheart, is that the "Long Necked" types actually represent sea slugs. An argument that favors this idea is that, unlike a mammal or reptile, a slug wouldn't need to surface out of the water to breathe and thus could remain undiscovered for much longer. The invertebrate nature would also explain the conspicuous lack of fossil remains of these animals.

In popular cultureEdit


  • The Sea Serpent, by Jules Verne (1901)
  • "A Tropical Horror", by William Hope Hodgson (1905)
  • The Maracot Deep, by Sir Arthur Conan Doyle (1929)
  • The Circus of Dr. Lao, by Charles G. Finney (1935)
  • Fantastic Beasts and Where to Find Them, by J. K. Rowling (2001)
  • The Loch, by Steve Alten (2005)


  • The Viking Women and the Sea Serpent (1957)
  • Reptilicus (1961)
  • Atragon (1963)
  • King Kong Escapes (1967)
  • The Sea Serpent (1984)

TV SeriesEdit

  • Adventures of the Gummi Bears
  • Dragons: A Fantasy Made Real
  • Hercules: The Legendary Journeys
  • Jake and the Never Land Pirates
  • Sofia the First
  • Time for Beany


See alsoEdit

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