The light needs to ripple with the water. Ripple edges, some dark spots in the main part. What happened to you is that the water is a flat object with bump height in the texture rather than a rippled object. You can either post render ripple it with Photoshop or remake the water with actual contours in it. Try a flat terrain with one of the PTE fractals in it. http://www.chesco.com/~cjcigas/tutorial/pte/