The hippo is the world's third largest land animal, weighing up to four tons. Although considered a land animal, they spend much of their lives in water. They eat, mate, and give birth underwater, as well as resting and sleeping.
Hippos can stay under over four minutes without coming up for air.
At dusk they leave the water in groups to forage for vegetation to satisfy their huge appetites. They can eat over a hundred pounds of food in a day. At Mzima Springs in Tsavo National Park, an observatory has been built below water level to see their underwater behavior.