One difference in taking photos as a snorkeler rather than a diver, is that I can’t follow fish when they dive or hug the bottom. Also, when a fish is 30 feet down, the water affects how they look and the sun doesn’t reach them as much.
I mention this because I most often see peacock groupers in 20 to 30 feet of water where they look somewhat dull in color. They also tend to be quite shy, hurrying for cover under ledges or whatever other shelter is at hand.
However, as with many kinds of fish, juveniles can often be found in shallower water. I happened on this young peacock grouper one day and it promptly headed for cover. Before it did though, I got a couple of good images that captured the sun bringing out the spectacular blue patterns that I never see when they run deeper.
In my attempts to identify what I see in the water, I use John P. Hoover’s book The Ultimate Guide to Hawaiian Reef Fishes, Sea Turtles, Dolphins, Whales, and Seals. His website is hawaiisfishes.com.