Blue marlin are the largest of the billfish, growing to 14 feet long and weighing up to a ton (the females are often significantly larger than males). They have distinct long bills, forked tail fins, and a first dorsal fin with a high initial crest that slopes sharply down and runs along most of the back. They are fast and powerful swimmers that prefer bluewater (open sea) where they can pursue schooling surface fish that they stun with their long bills.