Here you can see that I pushed the colors back on the farthest corals, eliminated the diver, added some spade fish and blue tangs and finally, added a foreground see turtle. I also pushed up some of the foreground colors.
This painting is for sale. 24" x 36" $1,500.
Here i have the background washed in with corals some reef structures. Don't be afraid to just start laying shapes in. You can always change them as you go. Also a pencil drawing can be useful to help layout the shapes before this step.