The Caloria indica is a fairly common but striking species of the Facelinidae family. We have found it crawling across the sand in water less than a metre deep, against a protected rock wall and in 20 ft of water on a algae covered exposed shelf.  Divers can find it to 60 metres.  It is relatively small (To 32mm, or 1.25″) and often hides amongst the hydroids it feeds on or in small crevices. It has a look-a-like which I have never seen.  If your creature has white-tipped rhinophores rather than orange-tipped ones, check out the Caloria #3.  For more info on the “indica” check out the Sea Slugs of Hawaii site.    Keoki Stender’s list of Facelinidae has also proved helpful when I’ve been trying to sort out subtle difference and possible relatives.