Have you ever come across a manatee? These friendly aquatic mammals are herbivores, grazing primarily on seagrasses and aquatic vegetation. Manatees have a fascinating history that spans millions of years. They are closely related to elephants and can be traced back to the Eocene era (about 56 to 33.9 million years ago). These slow-moving sea cows have, over time, adapted to life in warm, coastal waters.