Istiophorus platypterus, the Sailfish, is a species of billfish living in warmer sections of all the oceans of the world. They are predominately blue to gray in colour and have a characteristic erectile dorsal fin known as a sail, which often stretches the entire length of the back. Another notable characteristic is the elongated bill, resembling that of the swordfish and other marlins. They are therefore described as billfish in sport fishing circles. Sailfish grow quickly, reaching 1.2–1.5 metres (3 ft 11 in–4 ft 11 in) in length in a single year, and feed on the surface or at mid-depths. Individuals have been clocked at speeds of up to 110 kilometres per hour (68 mph), which is one of the highest speeds reliably reported in any water organism. Generally, sailfish do not grow to more than 3 metres (9.8 ft) in length and rarely weigh over 90 kilograms (200 lb). The sail is normally kept folded down and to the side when swimming, but it may be raised when the sailfish feels threatened or excited, making the fish appear much larger than it actually is. This tactic has also been observed during feeding. Sailfish are highly prized game fish and are known for their incredible jumps and great speed. They can swim 100 meters in 4.8 seconds. They can appear in a startling array of colours, from subdued browns and grays to vibrant purples and even silver. Their body colours are often highlighted by stripes of iridescent blue and silver dots. Sailfish can change their colours almost instantly—a change controlled by their nervous system. The sailfish can rapidly turn its body light blue with yellowish stripes when excited, confusing its prey and making capture easier, while signalling its intentions to fellow sailfish.