Dangerous Hippos; The kings of the African Rivers

What are these beautiful giant animals in many of the lakes and rivers called? Where do these hippopotamus live? Many times people wonder why such a big animals like the Hippopotamus to be as lazy as any other animal in the great lakes and rivers of Africa. Is being lazy part of the survival tactics for the hippo? As far as the animal facts about hippopotamus are concerned, the hippopotamuses or the "river horse” are the third-largest living land animals. Why the hippopotamus was called a river horse by the Greeks? Was it a hippopotamus fact that there were as many hippopotamus in Greece as compared to any part of the world or the hippopotamus population and range had reached far beyond the ancient Greek reign and hence the given name the “River Horse”?