I stumbled across an interesting phenomenon while trying to add a glisten to my dry lake bed.
I wasn't happy with the reflection shader (too plastic) so I tried plugging in the water shader and
my preview window started to show the water and the dry mud image.
Mind you it is an optical illusion Move the camera up or down (mainly down) and you can see the
contour of the terrain. But you can see through the water to the mud layer.
I have included a .tgc of the nodes and a screen shot. The dry mud image was too big to post (32 meg using 7-zip)
Hopefully it will be of some use to those bent on doing the impossible.