Photo of the Day 3 March 2008

Gentoo Penguins, Antarctica, 2006
Photograph by Paul Nicklen
Poised to plunge belly-first into the ocean, a colony of gentoo penguins lines up for a dip. Thanks to their sleek bodies and strong paddle-like flippers, gentoos are the world's fastest underwater swimming birds, reaching speeds of up to 22 miles an hour (36 kilometers an hour).