The definition between the two colours is very clear-cut. In shape and size this dolphin is stocky and grows to around 1.5 metres. Its appearance resembles that of a porpoise, but its conspicuous behaviour is typical of a dolphin. Their dorsal fin has a long, straight leading edge which ends in a curved tip. The fluke has a notch in the middle. This dolphin has no beak.

It is very active. It is often seen swimming rapidly on the surface and leaping from the water. It also spins and twists as it swims and may surf on breaking waves when very close to the shore. The Commerson’s Dolphin will bow-ride and swim behind fast-moving boats. It feeds on a mix of coastal and pelagic fish and squid. Those in the South American sub-population supplement their diet with crustaceans.

Females reach breeding age at 6 to 9 years. Males reach sexual maturation at about the same age. Mating occurs in the spring and summer and calving occurs after a gestation period of 11 months. The oldest known Commerson’s Dolphin died at age 18.