I just joined.. and have only just started warm water snorkeling/photography. Several trips to the Galapagos and a couple to St. John. Over 2000 underwater photos. I'm building a catalog of fishes I've seen. Using "REEF FISH" ... ",,Galapagos" and ",,,Florida Caribbean Bahamas" (P. Humann/N.Deloach" to learn. .. Oh, and reef.org and other onlines to try to identify fish.
This one has stumped me. It is a small fish. The urchin to the left is about 4"-6".... measured some. The only other image of the fish isn't as sharp as the light wasn't good and the photo blurred.