Hippos cannot swim because their bodies are too dense to float, they spend most of the day in the water. Hippos can stay underneath the water for about 6 minutes at a time Their eyes and nostrils are located high on their heads, which allows them to see and breathe while mostly submerged. A clear membrane covers and protects their eyes while allowing them to see underwater.A hippos small eyes, little ears and nostrils are placed high upon their heads – this enables the hippo to smell, see and breath while most of its body is submerged under the water.