[That's looking better already. It looks a little too vibrant to me, but that is something you'll be able to improve upon as you do it more and more. Notice the colors of the clownfish which seem too vivid - at least on my monitor. I think that image has a little too much red to it.
One guy on RC always posted images that were really dark, and several of us mentioned that to him. He decided to view the thread from his work computer and was shocked out how dark they looked. He then learned about calibrating his monitor from some of the photography experts on RC, and his images look much better now.]