I've always found Hippopotamus to be surprisingly intimidating. They're large swimming tanks with teeth. 
I think they look cute. They are mostly herbivorous semiaquatic mammals native to sub-Saharan Africa.
I might disagree with cute. Don't they like have loose stool and fling it everywhere with there tails to mark their territory? 
I've never seen them do that but it sounds wild. Their name comes from ancient Greek for "river horse".
I can believe that. I also heard they could snap alligators in half with their jaws.
They do have very powerful mandibles. Their closest living relatives are whales & dolphins.
Wow I don't think I knew that. I read that they also don't really swim and that the more of run along the bottom of the river. Is that true?
They can submerge for short periods of time but do have to breathe. They can actually run for short distances as well.