A sailfish is a fish of the genus Istiophorus of billfish living in colder areas of all Earth's seas, and holds the record for the fastest speed of any of Earth's marine animals. They are predominantly blue to gray in colour and have a characteristic 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.
