For such a small fish (about the size of your pinky finger) this guy has some decent teeth. Shooting a fish portrait with a macro lens you have to edge closer and closer, slowly. You need to gain the trust of the fish or it will just swim off and you won't get the shot. I think I took about 6 photos, each one getting a little closer until his face was almost hitting my port. I usually hold my breath from releasing bubbles (I don't recommend it, if not trained)
Shot whilst in the Mary Islands, Solomon Islands.
Canon 5D Mark III, Canon 100mm Macro, Aquatica water housing
1/250, F13, ISO 100