These tiny white Bulbaeolidia alba were all found in protected fish ponds or the shallow algae encrusted reefs of North Kihei, Maui.  At first glance they appear to be just another bit of shell or algae moving in the surf as they literally jerk across the rocks and algae covered rock.   On the surface they resemble the Bulbaeolidia paulae, but the latter lacks this jerky movement, and is often more colourful withmore abundant, more pronounced white-tipped cerata. For more images and taxonomic info check out the Sea Slugs of Hawaii site.  To about 9 mm, or less than 1/2 inch.