SEA hunpback photos, right and below Dall's and harbor porpoises are found throughout much of the Sound. Dall's usually travel in groups of up to 6 - 8, and they often approach moving boats to play in its wake. They can be identified at some distance by their characteristic crescent-shaped spray pattern when they surface, and once close to a boat, their black and white dorsal fin separates them from harbor porpoises. The latter are very shy, and are often solitary. Usually, the only thing one sees of a harbor porpoise is a brief glimpse of their dark back, bent in a wedge shape when they surface to blow.
Pinnipeds go ashore on rocky islets and headlands to breed and rest.
Northern, or Steller's, sea lions and harbor seal are common in the Sound. Both species have been a long-term population decline in Alaska, and the sea lion was recently placed on the endangered species list. Sea lions are distinguished from seals by their small external ears and their ability to rotate their rear flippers forward. Harbor seals' ears are small holes on the sides of their head, and they cannot rotate their rear flippers. Harbor seals are found throughout the Sound.