Nice work. The textures are pretty great already.

On the water, the biggest problem I can see is that it's very 'flat'. You've got great coloration in there. I'd suggest doing something to make the edges, especially in the 'walkable' areas differentiated from the floor. Maybe that means a slight bevel or maybe it means giving the floor some sort of slope down to the water surface. Because of the grid (I think) the floor looks almost like tile. If you're meaning for it to be sandy or rocky instead then I'd expect there to be a little bit of a slope along the bank of the river. Some more indications of flow might help as well, as you've done pretty well around that large flat rock.

Depending on how realistic you want to get you might also consider giving the water a bit of a surface. Filters like Plastic Wrap might be useful there.

Just some thoughts. Hope they help.
M