From krakens to serpents: 5 fearsome sea monsters from history

Sea monsters have haunted human imaginations for millennia. From the kraken to killer serpents, Prema Arasu explores what five mythical creatures reveal about our deepest fears

A large drawing showing multiple different sea creatures in a light blue ocean

Published: January 2, 2026 at 3:30 PM

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1. Armed and dangerous

The writhing tentacles of the kraken inspired horror and disgust

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Sea monsters have fired our imaginations – and chilled our blood – for as long as humanity has sailed the seas. The Babylonian epic Enūma Eliš, which dates back to at least 1200 BC, describes the creation of the world from two fearsome primordial beings: Apsû, the embodiment of subterranean fresh water, and Tiamat, the sea. Like the many mythical aquatic creatures that have occupied our dreams and our nightmares, Apsû and Tiamat reveal much about how the Babylonians saw the world, acting as projections through which their anxieties about nature could be expressed, examined and, perhaps, mastered.

Fast forward more than a thousand years and, in Naturalis Historia (c77 AD), the earliest extant work of natural history, the Roman author Pliny the Elder argued that the largest animals found in the sea “exceed in size any of the terrestrial animals” because of the “superabundance of moisture with which they are supplied”.

One such giant creature is the kraken, its origins lying in Nordic mythology and folklore. In his 1752–53 proto-scientific work The Natural History of Norway, Danish bishop Erik Pontoppidan described the “Kraken, Kraxen, or, as some world name it, Krabben” as an island-sized creature, “round, flat, and full of arms, or branches”.

Alfred, Lord Tennyson was so energised by reports of this monster of the deep that, in 1830, he wrote a poem in its honour, describing an ancient, giant-armed creature slumbering “Below the thunders of the upper deep; Far, far beneath in the abysmal sea.”

British naturalist Henry Lee offered a more rational perspective. In Sea Monsters Unmasked (1883), he stated that kraken sightings by sailors were most likely exaggerated reports of giant squid (Architeuthis dux), described a quarter of a century earlier by the Danish biologist Japetus Steenstrup.

Even after that, though, kraken and other squid-like monsters proliferated in literature. Herman Melville dedicated a chapter of Moby-Dick (1851) to the giant squid. Ishmael, Moby-Dick’s narrator, references The Natural History of Norway in his description of the creature, offering up the possibility that the kraken might not be a mythological beast but a taxonomically recognised species.

Myth and reality continued to amalgamate in the science-fiction genre. Jules Verne’s battle with a giant squid in Twenty Thousand Leagues Under the Sea (1869–70) was based on reports of an encounter between a French corvette, Alecton, and a squid in 1861. As Verne puts it: “Before my eyes was a horrible monster worthy to figure in the legends of the marvellous. It was an immense cuttlefish, being eight yards long… Its eight arms… were twice as long as its body, and were twisted like the furies’ hair.”

The uncanny undulations of kraken continue to fascinate. Roger Luckhurst, a scholar of the field of horror, links this to our innate “response to things that overwhelm our senses, stick too close, ooze across borders, or refuse to keep a stable shape”.

2. A feminine fantasy

Aquatic half-humans enchanted men and attracted women seeking new freedoms

Sirens, tritons, nereids, merfolk, nymphs… part-fish, part-human creatures have gone by many names over the millennia. These alluring beings have glided gracefully into cultural traditions across the world for thousands of years – particularly those with strong histories of seafaring. And, unlike many of the aquatic beings on these pages, they haven’t always done so with malign intentions.

In Naturalis Historia, Pliny described “tritons and nereids” as creatures in which “the portion of the body that resembles the human figure is still rough all over with scales”.

A stone relief showing a ship full of men sailing towards three women lined up on the left

A fourth-century BC urn shows Odysseus sailing towards the sirens, who, he reported, “sit and sing most beautifully in a field of flowers” (Image by AKG)

Sirens had appeared in Homer’s poem the Odyssey nine centuries earlier. But in the case of this ancient Greek epic, they were never physically described. Rather, we’re told that they “sit and sing most beautifully in a field of flowers”. Interestingly, they tempt sailors with knowledge, rather than – as other, later, depictions would have it – luring them to their doom. “When we had got within earshot of the land, and the ship was going at a good rate,” the fictional Odysseus recalls, “the sirens saw that we were getting in shore and began with their singing: ‘No one ever sailed past us without staying to hear the enchanting sweetness of our song – and he who listens will go on his way not only charmed, but wiser’.”

In medieval art, Homer’s sirens are interpreted as both aquatic and non-aquatic creatures. In contrast, the nereids of Greek myth were explicitly spirits or embodiments of the sea, albeit often visually depicted as human women. In the Romantic and Victorian imagination, they became synonymous with mermaids, frequently depicted with tails. Gothic writer Ann Radcliffe conjured a fish-tailed ingénue in her 1794 poem The Sea-Nymph, as did Hans Christian Andersen in The Little Mermaid four decades later.

A drawing showing a mermaid with a black, orange and yellow tail and long blonde hair, laying on her front on a rock, with a sea plant in the background

A 1930s depiction of Hans Christian Andersen’s Little Mermaid, which did so much to popularise the fish-tailed ingénue (Image by TopFoto)

Radcliffe’s poem marked a turn to the mermaid as a feminine fantasy: an aspirational symbol for young women who might otherwise feel confined by the gendered expectations of public life. This manifests today in the enduring visibility of the mermaid in popular culture and in the burgeoning pastime of mermaiding – cosplaying by swimming with a decorative monofin.

3. Terror in the deep

For millennia, giant, ravenous sea serpents have played on humanity’s primal terrors

It didn’t pay to get on the wrong side of the gods in ancient mythology. Just ask Laocoön, a Trojan priest who offended the deity Minerva – and didn’t live to tell the tale. As the Roman poet Virgil relates it in the Aeneid – his epic first-century BC poem telling the story of the foundation of Rome – Laocoön committed the cardinal sin of throwing a spear into the Greeks’ wooden horse to show that it was hollow. It was an act that so enraged Minerva that she unleashed two giant sea serpents to eat him.

“Taking swift course; their necks were lifted high,” Virgil writes of the ravenous creatures. “Their gory dragon-crests o’ertopped the waves; all else, half seen, trailed low along the sea; while with loud cleavage of the foaming brine, their monstrous backs wound forward fold on fold.” Poor Laocoön didn’t stand a chance.

As the priest’s grisly fate proves, the sea serpent had established itself as a terror of the deep by the time the Greeks and Romans dominated the Mediterranean. But they weren’t the first to live in fear of this creature. In fact, the ancient Greeks’ diverse bestiary of monsters likely derived from earlier prototypes. Sea serpents recur in the folklore traditions of a range of coastal and lake cultures, from the black, hairy Nile-dwelling monster Aman Doger of ancient Nubia to the rainbow snake of Australian Aboriginal Dreamtime myth.

An engraving showing a naked man with curly hair and a beard, with a large snake wrapped around his body, holding him down, alongside his two sons

Laocoön and his two sons are attacked by serpents, as shown in a 16th‑century engraving. Could megalophobia – the fear of large objects – be a factor in humanity’s obsession with sea monsters? (Image by Getty Images)

For the Victorian naturalist Henry Lee, tales of colossal sea serpents were a case of mistaken identity, likely originating in sightings of other marine phenomena – perhaps large pods of porpoises or whales. “I believe that… the supposed coils or protuberances of the serpent’s body, were only so many porpoises swimming in line in accordance with their habit before mentioned,” he wrote.

The anthropologist David D Gilmore has offered an alternative interpretation of our sea serpent obsession. He has suggested that the recurrence of such creatures in literature down the ages points to three primal human fears: of the sea; of what might lurk in the unknown; and of large objects, otherwise known as megalophobia.

4. The theory of de-evolution

Early Christians feared that the Leviathan would propel the human race back to its watery past

To some, it has been a benign presence. To others, a terror-inducing harbinger of doom. Ever since the Leviathan emerged from the depths of the oceans and floated into the human consciousness, it has meant different things to different people.

Jews and early Christians were certainly fearful. In the Hebrew Bible – where it appears in the Old Testament books of Psalms, Job and Isaiah – the Leviathan is a female sea serpent who will bring about the apocalypse together with her male counterpart, the desert monster Behemoth.

Such ancient beasts played on the enduring fear of regression, reminding us of our uncomfortable origins in the oceans. David D Gilmore suggests that the water that so often drips from primal monsters as they emerge from the deep “symbolises not only the amniotic fluids of the womb, but also the primal element from which all life emerged”. These creatures threaten us with the possibilities of de-evolution – a stripping of what modern science has decided makes us human.

A drawing depicting a large black whale being held under a boat, while several people and other sea creatures surround it in the water

An illustration from a 14th-century manuscript shows Alexander the Great being lowered into the sea to explore the ocean bed – a place populated by aquatic humans, dogs and a huge whale (Image by Getty Images)

For Renaissance cartographers, the Leviathan meant something different. Medieval maps of the world abound with monstrous-looking whales, depicted in ornate detail. According to historian Chet van Duzer, these illustrations served two purposes: to warn sailors of dangers that awaited them at sea, and as decorative elements designed to show off the artist’s talents.

By the time the American writer Celia Thaxter penned her poem Leviathan in 1876, the creature had shape-shifted again. For Thaxter, it was a largely peaceful presence, who triumphed against the rage of nature:

“For her worst fury he nor stayed nor turned.

‘Twas joy to think in such tremendous play,

Through the sea’s cruelty, all unconcerned.

Leviathan pursued his placid way!”

An illustration showing a large grey and orange fish with a man laying next to it, covered in flowers

A 14th-century depiction of Jonah with the giant fish that spat him out. Huge sea creatures make numerous appearances in biblical texts (Image by TopFoto)

5. Visions of Atlantis

Tales of an aquatic city populated by hyper-intelligent Atlanteans enchanted authors from Plato to HG Wells

“A strange vertebrated animal.” That’s how Elstead, the narrator of HG Wells’s 1897 short story In the Abyss, describes the lifeform he encounters on a journey into a deep ocean trench. “Two large and protruding eyes projected from sockets in chameleon fashion, and it had a broad reptilian mouth with horny lips beneath its little nostrils,” reported the intrepid submariner. “The vertical pitch of its face gave it a most extraordinary resemblance to a human being.”

In introducing Elstead to this strange creature, HG Wells was joining a long list of writers to conjure the inhabitants of a mysterious underwater civilisation into fictional life. In fact, the possibility of an intelligent, almost godlike race of aquatic beings living on the ocean bed has captured the imagination for centuries.

Mentions of the submerged island Atlantis date back to Plato’s fourth-century BC dialogues Timaeus and Critias, in which the Greek philosopher described a land sunken by a devastating earthquake. Renaissance scholars such as Francis Bacon linked Atlantis to the Americas, a notion he further explored in his utopian novel The New Atlantis (1624). In 1931, Woods Hole Oceanographic Institution scientists Henry Bryant and Columbus Iselin embarked upon a research cruise in search of the lost continent around the Azores. It was unsuccessful.

A photo of a woman with her hands pressed up against a glass tank, looking into the eyes of a large green sea creature behind the glass

2017 dark fantasy film The Shape of Water, which traces the relationship between a mute woman and a captured humanoid amphibian (Image by MovieStills)

Tales of Atlantis made a resurgence in the late 19th and early 20th centuries. Sir Arthur Conan Doyle’s 1929 novel The Maracot Deep features a team of scientists who descend into the ocean, become trapped in a deep-sea trench and are saved from disaster by descendants of Atlantis.

Other underseas peoples in popular fiction aren’t quite so benign. American horror writer HP Lovecraft described an undersea race of creatures called Deep Ones who worship the deities Dagon and Cthulhu. In The Shadow Over Innsmouth Lovecraft projects his own prejudices about racial purity and miscegenation (sexual relationships between people of different ethnic groups) onto a fictional coastal town. Here the residents interbreed with marine beings and become corrupted in form and character.

The denizens of cities under the sea continue to capture our imaginations today. Guillermo del Toro’s Oscar-winning 2017 film The Shape of Water tells how a mute cleaner working in a high-security government laboratory falls in a love with a green-skinned humanoid amphibian.

This enduring interest in aquatic beings speaks to a wider fascination with how great civilisations might fall. This is an intriguing and alarming prospect. After all, if a creature is to knock us off our self-appointed perch at the top of the evolutionary ladder, then surely that creature could come from the same primordial soup as we once did?

Prema Arasu is an adjunct research fellow at the University of Western Australia, and author of The Book of Sea Monsters: Leviathans of Literature (Adlard Coles, 2025)

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This article was first published in the Christmas 2025 issue of BBC History Magazine

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