The Kraken is a sea monster in the form of a giant octopus or squid, which is known for attacking ships. The exact size varies from the size of an island to roughly the size of a ship. While it does not always choose to attack ships, the force of it diving creates a massive whirlpool that can such ships down with it.
Bloop[]
In 1997, an ultra-low frequency underwater sound was detected by the U.S. National Oceanic and Atmospheric Administration several times. The sound, dubbed the Bloop, sounded similar to the emmision made by a Blue Whale yet the sound was carried over 5,000 km, suggesting it was made by a creature several times larger. The Bloop has been, somewhat humorously, associated with the Kraken.
Legends[]
Some legends say the kraken in the norwegian sea, others say it roamed the seas attacking ships.