We assume this animal is Volvatella viridis from its green shell and white animal, similar to specimens figured on the Sea Slug Forum. Gosliner et al (2018) figure an animal very much like this one, right down to the yellow margin at the anterior end of the shell, as Volvatella sp. 1. A single specimen measuring about 10mm was found in a clump of Caulerpa with its egg masses on a lagoon shipwreck at Kwajalein Atoll at a depth of about 17m on 14 May 2007.
An egg mass is present at the lower right side of the photo below.
Created 7 February 2007
Updated 4 December 2018