Cool I would say you need some caustic lighting from above. By that I mean take a semitransparent webbie looking .tif and use it as a gel on your lights. You could make a .tif like that by moving your camera above the surface of the water and rendering a .tif. Then take it to Pshop or your favorite. Make a greyscale image of it then use that as a gel for your light. this can help to give you that bottom of the pool lighting.