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.

Nudibranchs are blind to their own beauty, their tiny eyes discerning little more than light and dark. Instead the animals smell, taste, and feel their world using head-mounted sensory appendages called rhinophores and oral tentacles.

nudibranchs have hardly given up all their secrets. Scientists estimate that they've identified only half of all nudibranch species, and even the known ones are elusive. Most live no more than a year and then disappear without a trace, their boneless, shell-less bodies leaving no record of their brief, brilliant lives.