You need to adjust the environmental settings. In there the water can be adjusted to add some hue to it. On the route side, add in some bottom details and textures like sand and rocks. Dave Snow made some nice creek and river textures that work very well for this. You may also need to adjust the depth as well so that there isn't as much fall-off to black with the depth.
At least your water is black. Back in TRS2010, I ended up with clear water after a glitch that no one could solve and that issue finally fixed its self in TS12. The water was clear. Clear as air although it was there because there were some nearly transparent ripples.