hey man! I guess its water, isn't it? well, i gonna show you some hints
1. The colours are good, but you must try to use another more hmmmm... around grey-scale, you know haha
2. About the edge, in the shore, try to make it more rounded, and between the water and the sand (i guess its sand, yep?) i should put a white small border, as it seems to foam.
3. Another thing is the bright in the water. Try to use more contrastly brights, and it would work perfectly.
I hope I helped you bro. Good luck!