I think this is a blenny, possibly a goby still unable to find a reference to it, possibly colour variation or the head on composition is making it difficult to say for sure what it is.
Picture taken with Nikon D70s - Sea & Sea DX70 Housing - Two Sea & Sea Ys90 Strobes - Micro Nikkor 105mm - Nikon 4T Close-up Lens
It worthwhile trying a close-up lens, it does open up some areas of photography many ignore. Depth of field with this lens is particularly shallow and it often difficult to get even small subjects completely in focus. I was fortunate with this subject to get an even plane with subject.
This particular site was at the base of a large cliff and looked very promising from the surface, I personally found it difficult to find good subjects, and in the end was happy with this shot.
Location: Sardegna, Tedja (Tavolara)
Photographer: Robert Bailey