You will need the com edition or render to texture plugin
to use it.

In the one hand:

open MED:

File-> New Terrain--> change the count of vertics
--> Set a skin

Edit-->convert to Model--> Save


open WED:

Load a level and put this model into your Level.
Take it, and change a script.

-->Properties -->Behavior --> (template is: "fx_water_mirror")
--> change action


In the other hand:

Same like above, but without mirror.

Look for it in AUM 55.It s a fake mirror for water shader.