I like the water and the transparency. I think you should try to keep the sand slopes in mind and try to get a little bit more of surface variation for more realism :) To me it's very useful to start a layer with a very bright color, yelow for example, and then start to determine maximum height, slope, coverage, fractal noise, bump setting etc. etc. Then make lots of test-renders WITHOUT water (time) to judge the distribution and overall look. Then later change them into the desired colors and make some test-renders again. This is the way I've been learning TG myself, in a nutshell. Ik hope you may find some of these tips useful :) You can always IM me for questions.