Marlins are fish from the family Istiophoridae, which includes about 10 species. A marlin 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. Marlins are among the fastest marine swimmers. However, greatly exaggerated speeds are often claimed in popular literature, based on unreliable or outdated reports.