I’m afraid these photos are far from detailed or clear, but that has much to do with the fact that I had no idea what I was photographing.  While being thrown about in the surge zone, I thought I had come across another Berthella pellucida, a fairly common side-gilled sea slug.  Upon processing the image I noticed that it was not a pleurobranchidae at all, but rather some form of sacoglossia.  Its ultimate identification is still undetermined, but it is similar to the two documented on Sea Slugs of Hawaii.  25 mm in less than 2 metres of water, Makena Landing, Maui.