A marlin is a fish from the family Istiophoridae, which includes about 10 species. It has an elongated body, a spear-like snout or bill, and a long, rigid dorsal fin which extends forward to form a crest. Its common name is thought to derive from its resemblance to a sailor's marlinspike. Even more so than their close relatives, the scombrids, marlins are fast swimmers, reaching speeds of about 80 km/h (50 mph).
The larger species include the Atlantic blue marlin, Makaira nigricans, which can reach 5 m (16.4 ft) in length and 818 kg (1,803 lb) in weight and the black marlin, Istiompax indica, which can reach in excess of 5 m (16.4 ft) in length and 670 kg (1,480 lb) in weight. They are popular sporting fish in tropical areas.