This little Sacoglossid is very easily recognized by the reddish-orange tipped tentacles and very obvious orangeish, white and black spots that create a kind of saddle-back appearance to the parodia. According to the Sea Slugs of Hawaii site, Thuridilla sp. # 3 is fairly common, but in over ten years of searching I have only found one crawling across some algae in the broad light of mid-day.  The habitat was rock-strewn/heavy rubble, no more than a metre deep and stirred up with waves and sand near the shore of Ma’alaea Harbour, Maui.