Maybe some things to attempt with the water (I don't know to what degree each of these will work). Overlay a high opacity layer on the water using a filter--something subtle to distinguish some type of surface while still allowing the marble floor beneath to show. I'm not sure about the shadows around the pillars in water. It looks like maybe the shadows are resting on the "water" surface. Perhaps a more rippled, dark tinted shadow might work? I'm not sure? Maybe some type of surface reflection on the water.