Emperor penguins have an average swimming speed of 6.7 mph but have been observed swimming as fast as 8.9 mph. King and chinstrap penguin's average speed is 5.3 mph, while the fairy penguin swims much slower at only 1.6 mph.
To get the streamlined body shape needed to reach maximum swimming speeds, penguins hunch their heads into their shoulders and tuck their feet against their tails. Their wings act as flippers to propel them through the water. Their dense bones prevent them from being overly buoyant in the water. Most species of penguins stay submerged for less than a minute when diving.