Ever heard of the blue dragon?

If you heard about a tiny, funny-looking animal that spends its life floating upside-down on the surface of the Pacific, Atlantic, or Indian Ocean thanks to an air bubble which it swallows and keeps inside its belly, going wherever the currents and the wind take it, you would probably think it was just a harmless creature that likes to relax in the water. But this slender, up-to-3-centimeter-long animal, which is called the blue glaucus is not nearly as innocent as it seems.

http://en.wikipedia.org/wiki/Glaucus_atlanticus