These guys are pretty interesting. There's a couple different species, and frankly I'm not that good at telling them apart on the fly. This one is what we call a Peacock Razor Wrasse (Iniistius pavo). As a juvenile they'll have a very elongated first dorsal spine, oftentimes as long as the body of the fish, they tend to lose it (or keep it back and down) as they mature and it's much less noticeable. The adults are much more pale in coloration than the juveniles, this one's starting to be a "tweener" that's maturing.
We find Razor Wrasses generally in larger sand patches in the shallows, and below the reef in the sand at depth. They're not often easily approachable, as they tend to dive into the sand when you find them. It seems as though they have specific spots they "cultivate" in my opinion, 'cause sometimes they'll move as you approach then get to a spot and hover 'til you get too close and dive in. Interestingly enough, sometimes when you stick your hand in the sand it'll go through like nothing while the sand around it is much more firm. Anyway, these guys seem to have a knack for covering some distance under the sand as you can't dig them up (not that I've ever tried - it's hearsay, yeah that's it).
I used to have a Dragon Wrasse in an aquarium at home a half a life ago, these fish also dive into the sand on occasion and tend to sleep underground at night, mine had the habit of pulling up algae and piling it in one corner of the tank about 45 minutes before my lights were timed to go off and then it would dive into the pile and the oyster shell/dolomite mix for the night.
Pat took this photo, which is better than anything I have of Razor Wrasses, on a dive a couple months back.
We're off to do the manta dive tonight. Water conditions are quite decent today. I heard through the grapevine that there were 7 mantas seen off the airport last night.