To get fog effect in Poser, I have been advised to texture the Atmosphere :-

But in the resulting render, the resulting fogging is about the same all over, as if the camera's lens front was dirty, and does not get much more with distance to each object depicted as if the air (or here, water) was dirty or foggy. The relative sizes of the scuba divers (left) and the ditched jet fighter (right) show difference of distance.