Sailfish are a member of the family Istiophoridae and are easily identified by their distinctive cobalt blue, sail-like dorsal fin, which stands twice as high as the body is deep. The upper body is dark purple and the lower body is a paler silvery blue. The bill is long and slender and usually rough to touch. Sailfish generally feed on pilchards, yellowtail, tailor and other baitfish species.
Sailfish can reach a maximum length of 3.6 m and weight of 60 kg.
Sailfish are rarely found outside the tropics, but have been found in the more southern waters of Australia's east and west coasts during the summer months. They are pelagic, seasonally migratory fish.
Short-billed Spearfish (Tetrapturus angustirostris) and High-finned Spearfish (Tetrapturus audax) are sometimes confused with juvenile sailfish. However, Short-billed Spearfish can be distinguished by their dorsal fin, which is very much lower than that of Sailfish.