How to change normal map to unity water (pro) by script

HI I'm using this simple script attached to a button to change the Unity 4.6 water(pro) texture, it works in a regular material, but it doesn't seem to work in the water pro material. Any suggestions?

 var texture : Texture2D;
 
 var change : boolean = true;
  
  
 function changeTexture () {
  
         
        
                 renderer.material.mainTexture = texture;      
                 
                
         
 }