The top ten slowest animals in the world, ranging from fastest to slowest, are the manatee, Gila monster, nematode, seahorse, slug, koala bear, giant tortoise, garden snail, starfish and three-toed sloth. The three-toed sloth's top speed is 0.003 miles per hour.
Most of these animals are so slow because of their weight, their lack of muscle mass, their shells or their inefficient methods of locomotion.
The three-toed sloth is the slowest mammal on Earth because it lacks muscle tissue. It's built to live in trees and is often so slow that algae grows on its fur. The slowest bird is the American woodcock, which flies at five miles per hour, even during courtship displays. The slowest reptile is the giant Galapagos tortoise, which moves at 0.23 miles per hour on land, but is capable of moving much faster in the water. The slowest sea animal is the seahorse, which only moves at 0.01 miles per hour. Slow fish and sea creatures such as the seahorse and starfish learn to move more effectively by taking advantage of the water currents to move.
Finally, coral is an interesting contestant. It's one of the slowest animals as it's one of the few animals on Earth that do not move at all.