Came across this magnificent photo today via Digg.
It's a kind of tropical sea slug. Apparently "these animals float on the surface of the ocean being carried by the currents and the winds. Most of us are only aware of their existence when days of onshore winds blow great fleets of them on to the beaches, causing pain and angst for swimmers.
Both species spend their life floating upside down in the water, partially buoyed by a gas bubble in their stomachs."
Life is amazing.