Despite its massive bulk, this amphibious mammal moves underwater with grace, and trots on land with surprising speed. Indeed, the name hippopotamus (Hippopotamus amphibius), (Pronounciation: hip-oh-paw-TUH-muss AMM-fib-ee-us) means ‘river horse’, pertaining to this species’ semi-aquatic lifestyle. An extremely large animal with a round, barrel-shaped body, short legs and a large, broad head. The body is a greyish to muddy-brown colour on top and a pale pink colour underneath. The broad mouth can be opened extremely wide to expose large, curved canines, used in aggressive displays. The hippopotamus’ virtually hairless skin is moistened by a secreted pink, oily substance that protects the skin from sunburn and drying, and perhaps infection. A hippopotamus' nostrils are on the top of its head, so it can still breathe while almost totally submerged underwater.