The Nile Hippopotamus is a good swimmer and diver - even graceful under water. When submerged it closes its slitlike nostrils and ears. It stays submerged for 3 to 5 minutes at a time normally, but can stay under for 15 to 20 minutes if necessary. Hearing, sight and smell are all well developed, and all function with only the top of the skull above the water surface. The incisors and canines are tusk-like and grow continuously. The incisors are rounded, smooth, and widely separated. The barrel-like body is covered by short, fine hairs, but it appears naked. All four toes on each foot support the weight of the body. The skin is glandular and exudes droplets of moisture that contain red pigment. Light reflected through this appears red, giving it the name 'blood sweat.' The weight of males ranges from 3528 to 7056 lbs. Female weight is from 1444 to 5168 lbs. Birth weight is from 60 to 110 lbs.The young can swim before they can walk, and nurse under water.
The word 'hippopotamus' is Greek for 'river horse,' although this animal is not closely related to the horse at all.