Mostly, I find that fish don't like to be approached or chased. If you find a spot nearby and just sit there and wait, they'll usually come to you. Many fish are territorial. Watch and see what there favorite spot is. If they leave it and go elsewhere, wait at that spot. They'll be back in a few minutes. If there's a rock or a reef, wait behind it with your camera poised and focused on the edge. Snap them as they come around.