In Norwegian sea folklore, the Kraken is an enormous sea monster which would sometimes attack ships and feed upon the sailors. It was supposed to be capable of dragging down the largest ships and when submerging could suck down a vessel by the whirlpool it created. It is part octopus and part crab, although others refer to it as a giant squid or cuttlefish.
Aka : Krabben, Sciu-Crak, Hafgufe
Description
Probably no legendary sea monster was as horrifying as the Kraken, a giant sea monster. According to stories this huge, many armed, creature looked like an island when motionless and could reach as high as the top of a sailing ship's main mast with its arms deployed. When the Kraken attacked a ship, it wrapped its arms around the hull and capsize it. The crew would drown or be eaten by the monster. Kraken where mostly noticed in the seas of Scandinavia. Fishermen said that huge amounts of fishs gravitate around Kraken and the boat that succeeds to fish around the monster without awaking it will take more than possible to carry aboard.
Origin
The Kraken of legend is probably what we know today as the giant squid or cephalopod. Though they are considerably less then a mile and a half across, they are large enough to wrestle with a sperm whale.
Stories
Early stories about Kraken, from Norway in the twelfth century, refer to a creature the size of an island. Even in 1752, when the Bishop of Bergen, Erik Ludvigsen Pontoppidan, wrote his Natural History of Norway he described the Kraken as a "floating island" one and a half miles across. He also noted: "It seems these are the creatures's arms, and, it is said, if they were to lay hold of the largest man-of-war, they would pull it down to the bottom." Later Kraken stories bring the creature down to a smaller, but still monstrous size and assimilated it as a giant octopus.
On at least three occasions in the thirties they attacked a ship. While the squids got the worst of these encounters when they slid into the ship's propellers, the fact that they attacked at all shows that it is possible for these creatures to mistake a vessel for a whale.
From Monstrous.com