This tiny gymnodoris (less than an inch or 11 mm) has only been found once by our group of snorkelers and free divers — in an area where  Gymnodoris okinawae seem to dominate.  It was found in a few feet of water (less than a metre), in a protected area in North Kihei filled mostly with rock, sand and algae and sponge covered boulders.  Like other Gymnodoris they are fond of eating other nudibranchs.  See Sea Slugs of Hawaii for a photo of one devouring an Elysia degeneri.