Fastest animals
The fastest land animal is the cheetah, which has a recorded speed of . The peregrine falcon is the fastest bird and the fastest member of the animal kingdom with a diving speed of . The fastest animal in the sea is the black marlin, which has a recorded speed of .
Aquatic mammal
Aquatic mammals also display a variety of locomotion styles. Cetaceans excel in streamlined body shape and the up-and-down movements of their flukes make them fast swimmers; the tucuxi, for example, can reach speeds of . The considerably slower sirenians can also propel themselves with their fluke, but they can also walk on the bottom with their forelimbs. The earless seals (Phocidae) swim by moving their hind-flippers and lower body from side to side, while their fore-flippers are mainly used for steering. They are clumsy on land, and move on land by lunging, bouncing and wiggling while their fore-flippers keep them balanced; when confronted with predators, they retreat to the water as freshwater phocids have no aquatic predators.
Some aquatic mammals have retained four weight-bearing limbs (e.g. hippopotamuses, beavers, otters, muskrats) and can walk on land like fully terrestrial mammals. The long and thin legs of a moose limit exposure to and friction from water in contrast to hippopotamuses who keep most of their body submerged and have short and thick legs. The semiaquatic pygmy hippopotamus can walk quickly on a muddy underwater surface thanks to robust muscles and because all toes are weight-bearing. Some aquatic mammals with flippers (e.g. seals) are amphibious and regularly leave the water, sometimes for extended periods, and maneuver on land by undulating their bodies to move on land, similar to the up-and-down body motion used underwater by fully aquatic mammals (e.g. dolphins and manatees).