Nudibranchs are unbelievably cool, with vibrant colours and odd shapes they really do look like aliens of the ocean. They are, in fact, a type of mollusc, which includes clams, snails, and octopus. Their name in latin means naked gills, which is what gives them the strange body forms as the gills take different shapes on their sides and back.
So aside from the fact that they look awesome, what makes a nudibranch special? There are currently over 3 000 known species, and new ones are constantly being discovered. They can range in size from about six millimeters (a quarter of an inch) to 31 centimeters (12 inches). They are hermaphrodites, so any mature individual can mate with any other mature individual from the same species. And would you believe they are carnivores? They will eat algae, sponges, anemones, corals, barnacles, and each other.
You are what you eat is true for a nudibranch. Their vibrant colours generally comes from the food they eat, and some of them can use the poisons found in their prey as a defense against their own predators.
Some of them can actually store algae in their outer layers and live off the sugars that the algae produces during photosynthesis.
All I can say is awesome!
Check out http://www.oceanshutter.com/ for more cool ocean videos.