The name "hippopotamus" comes from Greek words meaning "water or river horse," but hippos are not related to horses at all—their closest living relatives may be pigs or whales and dolphins. They are built for life in the water: their eyes, ears, and nostrils are on top of their head. They can see, hear, and breathe while most of their body is underwater.
Hippos don't float or swim. They move around in the water by pushing off the bottom of the river with their feet. If you saw it underwater, it would look like the hippo was walking or running. If they need to, adult hippos can hold their breath for up to 30 minutes.
To protect their skin from the hot sun, hippos ooze a thick, red goo called "blood sweat" out of their pores. It works like sunscreen, and may even keep cuts and scratches from getting infected.