Manatee

The Saltwater Cow: The manatee, often called the sea cow, is the only exclusively herbivorous marine mammal. It grazes on all kinds of aquatic plants, especially marine sea grasses, assisted by its large prehensile lips, which are studded with bristles.

Surface Dweller: During the day, the manatee is frequently found close to the surface, sleeping within the top 3 to 10 feet. Occasionally it swims down to 30 feet, propelling itself along with the aid of its large flat tail, which it also uses as a rudder. When feeding, which it usually does at night, the manatee walks along the bottom using its forelimbs.

Warm Water Only: It is restricted to tropical and subtropical waters because it has an unusually low metabolic rate for a large mammal and rapidly loses body heat to the surrounding water.