The sperm whale is the world's largest carnivore. It can grow to a length of more than 60 feet, and has a huge boxlike head that makes up more than one-third of its total length. It is an impressive diver, plunging to depths of nearly 4,000 feet and staying submerged for almost two hours at a time. The sperm whale is found in deep waters worldwide and is threatened by hunting, being caught in fishing gear and colliding with ships.