Penguins, unlike fish, are warm-blooded animals, yet they manage to keep warm in the freezing temperatures of their natural habitats. Part of this is due to a layer of blubber, essentially fat, insulating them from the cold, but the main contributing factor to their warmth is the air bubbles that form under their feathers. By puffing up these short, stiff and uniformly distributed feathers, penguins create a layer of air surrounding their body, protecting them from the cold. They can also trap these feathers down when swimming to create a watertight barrier.
By studying the structural arrangements of these feathers as well as their mechanical properties, engineer are trying to mimic the insulation capabilities displayed by penguins. Man-made insulation works on the same principle: trapping a foam-like structure between structures like glass or ceramic; insulative paints also exist. Nevertheless, try as they might, engineers haven't matched penguins' feathers in terms of insulation, water tightness, and mechanical properties .