Ok last waterfall, This one is a MDL7 format.
All you have to do is use the default fx_uvspeed action that is supplied
with GS. Settings are Passable, Transparent and set speed_v to -5.000.
I don't know which earlier versions of GS this will work with.
I also included the dodgey waterfall jet model as well.
Here is the pic.
Here is the download link.
The models in RAR format Please enjoy..