Orcas are distinctively marked with a black back, white chest and sides, and a white patch above and behind the eye. Calves are born with a yellowish or orange tint, which fades to white. Orcas have a heavy and stocky body and a large dorsal fin with a dark grey "saddle patch" at the fin's rear. Antarctic Orcas may have pale grey to nearly white backs.
The Orca's large size and strength make it among the fastest marine mammals, often reaching speeds in excess of 56 km/h (35 mph. Unlike most dolphins, the pectoral fin of an Orca is large and rounded, more of a paddle than other dolphin species. Males have significantly larger pectoral fins than females. At about 1.8 m (6 ft), the male's dorsal fin is more than twice the size of the female's and is more of a triangular shape, a tall, elongated isosceles triangle whereas the dorsal fin of the female is shorter and generally more curved.