The colors are nice and exposure is good but a 105mm macro would have been a better lens choice, the subject is much to small in the frame and also heavily obscured. The shallow depth of field casing the blurred obstruction and the subject being so small causes no impact for the viewer. I would suspect 99% of the non UW photographic populatation would not have a clue as to what they were looking at. On the positive site the colors are compelling to keep them looking while they scratch their heads.
Both the 60mm and 105mm macro lenses focus to 1:1, and i think this image is shot at near 1:1 from looking at the soft coral., and thus the 105mm would have made no difference to the size of the cowrie in the frame. The 105mm would have given you more working distance though.
If you really want to shoot the tiny stuff like this at full frame then you'll need some teleconverters and probably the 105mm to give you the increased working distance, but then you will be diving a very specialised dive, and you are bound to see manta rays and whale sharks whilst you are stuck in super macro mode!
The position of the cowrie isn't conducive to good composition, maybe next time take a couple of shots, then have a look around at some other stuff and come back later on to see if it had moved?
Did you bracket with some different composition? maybe post those too so we can take a look.
The exposure is good and i like the colours, but sometimes the critters aren't in a photographic mood and all we can take is a snapshot, it's still a nice shot for ID purposes though.
May i also suggest that you look at some other image hosting sites as that one has watermarked your image, and doesn't seem to give a link to your album. Flickr is a popular one.
I hope this helps!