This seems closest to the Liloa mongii figured on the Sea Slugs of Hawaii site, differing only in minor coloration details on the animal. The 15mm animal below was found by Christina Sylvester on a shallow water sunken landing craft on the lagoon side of Kwajalein Island.
The one below was on an eastern lagoon sandy reef.
Created 20 March 2017
Updated 5 April 2023