A couple of months ago, Betty & I were diving together when she pointed out a roundish mass of gunk to me. I didn't think much of it as it appeared to be some kind of encrustation like a sponge or something. However, it was very slowly moving which prompted me to get out the camera and take some photos.
Photo Copyright 2012 by Barry Fackler
Anyway, I went home and downloaded the photos and looked at all the colorful and interesting stuff I had captured. Weeks later, while checking my book on marine invertebrates to identify something else, I saw a familiar image. It was the "mystery creature" which turned out to be an umbrella slug (Umbraculum umbraculum). Hoover's book, Hawai'i's Sea Creatures, says "this large, sponge-eating, side-gilled slug carries a calcareous disc too small to cover itself completely". The entry goes on to say that the species has a wide Indo-Pacific and tropical Atlantic distribution but is uncommon in Hawai'i. So, Betty came up with an unusual and remarkable find!