Water mammals are aquatic animals that live in the water and breathe air. Two of the most common water mammals are the otter and the WHALE. Otters are small, semi-aquatic mammals that have a long, slim body and webbed feet. They are found in rivers, lakes, and oceans all over the world. Whales are large aquatic mammals that live in the ocean and breathe air through a blowhole on the top of their head. They are known for their long migrations and their loud songs. Dolphins are also aquatic mammals that live in the ocean and breathe air. They are known for their intelligence and playful behavior.