Blue shark (Prionace glauca), Faial-Pico Channel, Azores Islands, Portugal. The blue shark is a species of requiem shark, in the family Carcharhinidae, that inhabits deep waters (images taken though between 5 and 10 meter below water) averaging around 3.1 m (10 ft) and preferring cooler waters. They can live up to 20 years, can move very quickly and feed primarily on small fish and squid, although they can take larger prey.