One clue can be found in the many forms sea monsters take. According to myth and legend, such creatures range from the gigantic to the human-sized, from the fanciful to the almost familiar.
In the latter category we come across the Scandinavian sea monster called the kraken, the subject of tales dating back to 1180 and the inspiration for a poem by Alfred, Lord Tennyson (see sidebar). The creature, perhaps inspired by actual sightings of giant squids, reputedly dwelled in the waters off Norway and Iceland. Legend says it measured more than 1.5 miles (2.5 kilometers) across and sported arms the size of ship's masts. Indeed, the beast was reputedly so vast that sailors could mistake its body for land or its tentacles for a ring of islands. As a result, the greatest danger it posed was the whirlpool it created while surfacing or submerging [source: AMNH].
Other familiar creatures that assumed monstrous proportions in legend included giant sea serpents and gargantuan turtles [source: Haven].
Far more than mere curiosities or threats, sea monsters often played a vital symbolic or religious role in cultures around the world, some of which viewed them in a more neutral or positive light. In Hinduism, the makara -- a half-animal, half-fish -- transported Ganga, the goddess of the river Ganges, and Varuna, the god-sovereign of Vedic Hinduism, who is also linked with oceans and waters. The Chinese viewed most dragons as benevolent and associated them with good luck and procreative power [source: Morell]. On the other hand, in Native American stories, the giant water creatures called unktehila represent the world's evils and must be defeated by the Wakinyan, or Thunder Beings.
On a smaller scale, sea monsters could assume the form of dangerous, often enthralling, mer-humans or animals. For example, Scandinavians and Scots alike spoke of horse-like, shape-shifting kelpies that lured children to watery graves.
Myths and religions also named specific sea monsters. We've already discussed Tiamat, the many-headed dragon goddess of the primordial sea, and the Old Testament creature Leviathan, who scholars believe was influenced by her [sources: Barré; Encyclopaedia Britannica]. The Greeks gave us another such monster, named Cetus by the Romans and enshrined as a constellation. Poseidon sent Cetus to destroy the kingdom of King Cepheus as punishment after Cassiopeia, his wife, boasted that her daughter was more beautiful than the sea nymphs. The creature -- which is named after the Latin word for whale but is usually depicted as having paws, a doglike head and a curling fish tail -- rampaged through the kingdom until the royal couple offered the daughter, Andromeda, as a sacrifice. Perseus famously slew the creature and saved her.
Such tales form an essential component of cultures the world over. They enrich our languages with symbol, metaphor and, in some cases, belief. But why do we fall for them hook, line and sinker?