The blue shark (Prionace glauca) is a species of requiem shark, family Carcharhinidae, that inhabits deep waters in the world's temperate and tropical oceans. Preferring cooler waters, blue sharks migrate long distances, such as from New England to South America. Although generally lethargic, they can move very quickly. Blue sharks are light-bodied with long pectoral fins. Like many other sharks, blue sharks are countershaded: the top of the body is deep blue, lighter on the sides, and the underside is white. The male blue shark commonly grows to 1.82 to 2.82 m (6.0 to 9.3 ft) at maturity, whereas the larger females commonly grow to 2.2 to 3.3 m (7.2 to 11 ft) at maturity. The blue shark is an oceanic shark found worldwide in deep temperate and tropical waters from the surface to about 350 meters. In temperate seas it may approach shore where it can be observed by divers, while in tropical waters it inhabits greater depths. It prefers waters with a temperature range of 7–16 °C (45–61 °F) but will tolerate temperatures of 21 °C (70 °F) or above.