Mammals with flippers include whales and seals. Whales are large aquatic mammals that live in the ocean and have a streamlined body, a blowhole, and flippers. The most common type of WHALE is the killer WHALE, which has five letters in its name. Seals are smaller aquatic mammals that live in the ocean and have four letters in their name. They have a streamlined body, flippers, and a thick layer of blubber to keep them warm in cold water.