I have always loved manatees, and I guess it's because I've read so much about how gentle they are. Most sea animals of this size could be dangerous, but these creatures are dubbed gentle giants. In fact, they are actually drawn towards humans swimming or diving in water.
They are only one of two species of underwater mammals who are herbivores. All the rest of the underwater mammals are carnivores, so this make these animals so unique. They eat plants under the water, but will sometimes surface and eat leaves off of trees.
I put in a picture--what do you think?
Photo credit: By pelican from Tokyo, Japan (Toba aquarium, Mie, Japan) [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons