1. The Name Means "Water Horse": The word "hippopotamus" comes from an ancient Greek phrase that literally translates to "river horse," even though hippos are actually much more closely related to pigs, cows, and even whales than they are to horses!

2. The Name Means "Water Horse": The word "hippopotamus" comes from an ancient Greek phrase that literally translates to "river horse," even though hippos are actually much more closely related to pigs, cows, and even whales than they are to horses!

3. True River Couch Potatoes: Hippos are semi-aquatic animals, meaning they spend up to 16 hours a day completely submerged in rivers, lakes, and muddy swamps to keep their giant bodies cool under the blazing sun.

4. Underwater Breath-Holders: Even though they love spending time underwater, hippos can't breathe down there. They can hold their breath for about 5 minutes at a time, and they even have special valves in their noses and ears that automatically snap shut when they dive!

5. The Second Heaviest Land Mammal: Hippos are absolute heavyweights! An adult male hippo can weigh up to 4 tons (8,000 pounds), making them the second heaviest land animal on Earth, right behind the massive elephant.

6. Gargantuan Jaws and Chompers: A hippo's mouth is huge, and they can open it astonishingly wide—up to an incredible 180 degrees! Inside, they have enormous, tusklike teeth that can grow up to 2 feet long, which they use for defending their territory.

7. Nighttime Grass-Munching Buffet: After spending the hot daylight hours snoozing in the water, hippos waddle out onto land at night to graze on grass. A single hungry hippo can eat around 80 pounds of grass in just one night!