(species Regalecus glesne), large, long, sinuous fish of the family Regalecidae (order Lampridiformes), found throughout the tropics and subtropics in rather deep water. A ribbon-shaped fish, very thin from side to side, the oarfish may grow to a length of about 9 m (30.5 feet) and a weight of 300 kg (660 pounds). It is shiny silver in colour, with long, red, oarlike pelvic fins and a long, red dorsal fin that rises as a manelike crest on top of the head. Seldom seen at the surface, it is credited as the “sea serpent” of some reported sightings.