A penguin is a type of bird that can fly under water but not in the air. Penguins are mostly found north of the equator in cold climates. They use their wings as flippers to swim under water and catch fish. The biggest penguins are about the same height as you and your classmates. The smallest penguins are 13 inches tall, which is only 1 inch longer than a sheet of paper. They must be pretty cute!