i can confirm that fx_water_mirror will work fine with A7 comm. a couple of things to double check maybe..

• Use a flat terrain .hmp file with at least 32 verticies in x and y directions
  
• Assign a bump map texture to skin 1 of the terrain. There is a good bump located in your 3dgs install at "template_6\images\waves.dds"
  

That should be all you need to get things going. I always add a skybox in the level just to give me some bearings to the world, plus it keeps the background from smearing when moving making it harder to tell what is really going on. hope that helps!