"During the night two porpoises came around the boat"
Dall's porpoise
Creative Commons AttributionDall's porpoise, type of porpoise found in the North Pacific - Credit: Travis S.

Porpoises, like dolphins and whales, are marine mammals--that is, they are warm-blooded and give birth to live young. They are generally smaller than dolphin—"seldom more than six feet (1.8 m) long—and [have] a blunt muzzle instead of a pointed one."