Zim Hunters Guides Forum

Hippos are more like underwater walkers than swimmers! They don’t actually swim—at least not in the way most animals do. Instead of propelling themselves through water using their limbs, they walk or run along the riverbed. Their bodies are extremely dense, so they stay submerged but can push off the bottom to move forward.
They can also hold their breath for about 5 minutes and even sleep underwater, using a reflex that lets them bob up for air without waking up.