How do penguins stay warm in freezing water?

Penguins keep warm because their bodies slow heat loss from several sides at once. Fat beneath the skin stores warmth, tightly oiled feathers shed water, and a soft inner feather layer holds air next to the body, so icy seawater has a hard time reaching bare skin.

Their feet and flippers can stay much cooler than their middle because blood vessels narrow during a dive. Nearby arteries and veins trade heat before blood returns inward, and on land emperor penguins take turns at the outer edge of the crowd.