Well, I can see a few problems. 1) No apparent reflection 2) No apparent refraction 3) No displacement 4) You can see the sky under the water (as opposed to reflecting on the surface) I suspect you are rendering against a background.. might be better to put your JPG on a square or something similar. Try turning on reflection, refraction, and displacement. The BASE of the material (colors, appearance, etc) looks pretty darn good. I think you just need to do some fine tuning.