Sailfish grow quickly, reaching 1.2–1.5 m (3 ft 11 in–4 ft 11 in) in length in a single year, and feed on the surface or at middle depths on smaller pelagic forage fish and squid. Individuals have been clocked at speeds up to 110 km/h (68 mph), which is one of the highest speeds reliably reported in any water organism. Generally, sailfish do not grow to more than 3 m (9.8 ft) in length and rarely weigh over 90 kg (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, when a group of sailfish use their sails to “herd” a school of fish or squid.
Ernest Hemingway in Key West, Florida, USA, in the 1940s, with a sailfish he had caught
Sailfish are highly prized game fish, and are known for their incredible jumps and great speed. They can swim 100 m in 4.8 sec. 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.