There is a note in a ship's log from HMS Daedalus, dated August 6, 1848, approximately two hundred miles off the coast of St. Helena, in which Captain Peter McQuhae and six members of his crew describe watching a creature moving through the water alongside them for roughly twenty minutes. The creature, they write, had a head approximately four feet in length, held eighteen inches out of the water, and a body visible beneath the surface for something like sixty feet. It was dark brown on top and yellowish-white on the throat. Its speed, they estimated, was about twelve to fifteen miles an hour. It did not slow down, and it did not turn to look at them.
The Captain's sworn report, filed with the Admiralty three months later, produced one of the most famous sea monster incidents of the nineteenth century. It was reprinted in the Illustrated London News, debated in scientific journals, dismissed by Sir Richard Owen as probably a misidentified sea-elephant, and, quietly, never retracted. Six British naval officers, working professionals with long careers, signed their names to the account. Whatever they saw, they believed what they were reporting.
Sea monsters are one of the most durable categories in world folklore. They outlast most of the empires that wrote about them, most of the religions that tried to interpret them, and most of the natural philosophies that tried to rationalize them. What I want to do here is catalog the four or five large and persistent sea-monster traditions of the European and Mediterranean seas, show where each one came from, and offer what the modern record suggests was actually being seen.
The Kraken, and what is probably in the water
The earliest detailed description of the Kraken that I can find in the archival record is from a Norwegian bishop named Erik Pontoppidan, writing in his Natural History of Norway in 1752. Pontoppidan, who was a serious scholar and not a fabulist, describes the Kraken as approximately a mile and a half in circumference, living on the sea floor, surfacing occasionally to feed, and producing whirlpools when it submerged that could pull down ships. His sources were Norwegian fishermen, whose testimony he regarded as reliable enough to publish under his own name.
The Kraken tradition Pontoppidan recorded was, by then, already old. Icelandic sagas reference something similar, the hafgufa, from at least the 13th century. The Greek poet Homer describes something comparable in the Charybdis of the Odyssey. What the Norwegian Kraken added to the older tradition was specificity: a size, a habit, a habitat.
The modern answer to what Pontoppidan was hearing about is almost certainly the giant squid, Architeuthis dux, which was confirmed as a real species only in 1857 when a Danish zoologist named Japetus Steenstrup described one that had washed ashore. Giant squid can reach fourteen meters in length. They live at depth, surface rarely, and are occasionally seen by fishermen in conditions that would produce exactly the kinds of reports Pontoppidan collected. The whirlpool stories were almost certainly ordinary tidal phenomena being narratively attached to the creature by people who needed an explanation for what had sunk their boats.
The giant squid did not discredit the Kraken. What it did was give the Kraken a biological address. The creature that had existed for four hundred years in folklore turned out to have existed the whole time in zoology.
Leviathan, which was never really a creature
The biblical Leviathan is often grouped with the Kraken in popular accounts, and this is a mistake. The Leviathan of the Book of Job, chapter 41, is not a folklore monster in the sense that the Kraken is. It is a theological figure, an illustration used by the book's author to make a specific argument about the limits of human power and knowledge. The creature described has scales, fire-breath, and a body impervious to human weapons. No sailor ever claimed to have seen one.
What the Leviathan did do, culturally, is provide a vocabulary. When later authors, including the seventeenth-century political philosopher Thomas Hobbes, needed a figure for overwhelming, uncontrollable power, the Leviathan was available. When medieval bestiarists needed a symbol for the ultimate sea-creature, the Leviathan was there. The actual reports of sightings, though, are much thinner than one might expect. Leviathan was an idea about the sea, not a report from it.
The Leviathan was an idea about the sea, not a report from it. The Kraken was a report from it, even if the report was wrong.
The sea serpents of the nineteenth century
Between roughly 1800 and 1900, a particular subgenre of sea monster sighting produced more reports than any other period before or since. The reports came from trained naval officers, from merchant captains, from passengers on transatlantic liners. The creatures described were remarkably consistent: long, serpentine, moving through the water with visible undulations, often with a head held several feet above the surface. The Daedalus report of 1848 is the most famous. It is one of hundreds.
Several things were probably going on. Some reports, including the Daedalus, may have been misidentified basking sharks or oarfish. The oarfish, Regalecus glesne, can reach eleven meters in length, lives at depth, and surfaces only when sick or dying. A sick oarfish on the surface, seen from two hundred yards away through a telescope, produces an almost exact match for what Captain McQuhae described. Other sightings were probably whales, or strings of porpoises moving in line, or debris. A small number were probably deliberate hoaxes.
But the sheer volume of reports, from disparate witnesses who had no contact with each other, suggests that something additional was going on. I would hazard the following: the nineteenth century was the first period in which large numbers of educated, literate, non-specialist observers were spending long periods at sea, reading about sea monsters in newspapers, and then writing up their own sightings for the same newspapers. The feedback loop was not the cause of the sightings, but it was the cause of their form. People saw strange things at sea because strange things were, and are, genuinely present at sea. They described them in sea-serpent terms because sea-serpent terms were the terms available.
The Irish merrow and the smaller sea monsters
Not all sea-creature folklore was of the continent-scaling variety. The Irish tradition of the merrow, which is essentially a localized mermaid, is documented in ballads and court records from the 14th century onward. Merrows were said to come ashore, marry human men, raise children, and eventually return to the sea. Several Irish families trace their genealogy to merrow ancestors, and the claim is taken seriously enough to appear in genealogical records as late as the 18th century.
The merrow tradition almost certainly mingles with seal folklore, particularly the Scottish selkie, and the two are functionally difficult to separate. What both traditions are doing, anthropologically, is providing a category for the not-quite-human, the neighbor who came from elsewhere and could, at any time, return elsewhere. The selkie story is about the precariousness of domestic life in coastal communities where men went to sea and sometimes did not come back. The sea, in these stories, is not a thing that monsters live in. It is a thing that takes people away.
What remains
Modern oceanography has, in one sense, eliminated the sea monster. We know what lives in the ocean. We have photographed the giant squid alive, in its native habitat, as recently as 2012. There is no Kraken the size of an island. There are no sea serpents three hundred feet long. There is, at most, a somewhat larger giant squid than the one in the zoology textbook, and a colossal squid, Mesonychoteuthis hamiltoni, slightly larger still.
In another sense, the sea monster is doing fine. What the sailors were actually reporting, when they signed their names to sea-serpent sightings, was the feeling of being small on a large and indifferent body of water, watching something move past your ship that did not care that you were there. That feeling has not been disproven. It has, if anything, gotten larger. The sea is still mostly dark, mostly unexplored, and mostly full of creatures we have not yet photographed. The odds that there is something down there we have not catalogued are, statistically, roughly one.
The sailors are still out there, is what I mean. They are just not allowed to file sworn reports about it anymore.