The Black Spot Nudibranch (Joruna funebris) is a fairly common species throughout the Indo Pacific, but is a relatively new species to Hawaiian waters. It is certainly not one that we see very often.  The individual here was found in sand, in only a few feet of water as the photographers were exiting a beach in North Kihei, Maui.  The only other white and brown/black spotted sea slug that we have seen in Hawaiian waters is the Euselenops luniceps but it is significantly larger, has tube like rhinophores and lacks  branchial gills.  For more information and photos, check out Cory Pittman and Pauline Fiene’s  Sea Slugs of Hawaii site.  To just over 2″ (60 mm).