Check out the recent National Geographic article on nudibranchs (small colourful snail-like invertebrates that inhabit coral reefs) – there are some astounding images of these fascinating underwater creatures (link to photo gallery).
Nudibranchs crawl through life as slick and naked as a newborn. Snail kin whose ancestors shrugged off the shell millions of years ago, they are just skin, muscle, and organs sliding on trails of slime across ocean floors and coral heads the world over.
Found from sandy shallows and reefs to the murky seabed nearly a mile down, nudibranchs thrive in waters both warm and cold and even around billowing deep-sea vents. Members of the gastropod class, and more broadly the mollusks, the mostly finger-size morsels live fully exposed, their gills forming tufts on their backs. (Nudibranch means “naked gill,” a feature that separates them from other sea slugs.) Although they can release their muscular foothold to tumble in a current—a few can even swim freely—they are rarely in a hurry. (Read More)