Sperm Whale in the deep sea.

The sperm whale, known to science as Physeter macrocephalus, is the largest of the toothed whales, which includes other members such as the dolphin and killer whale. These whales get their name from the oily fat, known as spermaceti, which is contained in their large heads. It is because of this substance and the oil from the whale's blubber that these majestic animals where viciously hunted by whaling boats. In older times, sperm whales were known as common cachalot, which was an old French word for "tooth". As with all whales, sperm whales are mammals and require air to breathe. They are one of the deepest diving mammals in the world, and are able to stay underwater for up to two hours before coming up for air.

The sperm whale can grow to a length of 67 feet (20.5 meters) and weigh over 63 tons (57,000 kilograms). Sperm whales are one of the most sexually dimorphic of all the whale species, meaning that the males and females differ greatly in size and weight. The males are generally 30% to 50% larger than the females. The whale's large head accounts for up to two-thirds of the animal's total length, and it has the largest brain of any animal in the world. Unlike most other whales, which have smooth skin, the skin on the back of the sperm whale is rough and wrinkly. In fact, it has been compared to that of a prune by many whale watchers. The sperm whale does not have a pronounced dorsal fin on its back. Instead, it has a series of ridges, the largest of which resembles a small hump. The color of these whales is usually a uniform gray, although they sometimes look more brownish-gray in sunlight. White albino whales have sometimes been observed in the wild.