sailfish

thumb|An Indo-Pacific sailfish raising its sail thumb|upright|Author Ernest Hemingway in [[Key West, Florida, USA, in the 1940s, with a sailfish he had caught ]]

The sailfish is one or two species of marine fish in the genus Istiophorus, which belong to the family Istiophoridae (marlins). They are predominantly blue to gray in colour and have a characteristically large dorsal fin known as the sail, which often stretches the entire length of the back. Another notable characteristic is the elongated rostrum (bill) consistent with that of other marlins and the swordfish, which together constitute what are known as billfish in sport fishing circles. Sailfish live in colder pelagic waters of all Earth's oceans, and hold the record for the highest speed of any marine animal.