Consider using volumetric lighting effects, so that the light doesn't go too deep into the water. Poser 4 users had to add partially transparent planes to get the same effect. In P5 you could use a shader node to give such a layer a varied transparency, and make the water less uniform. I think you're right that your posr #12 is a little too transparent, but that can be scene-dependent You've got a location which feels as if the water should be a bit murky.