Check out
this thread. We got pretty deep on the subject of headlights there.
If you have water in your headlight assy, you could try pulling one of the lights out and allow the sun to bake the water out. Removing the light allows for better convection inside the headlight assy. There will still be some fogginess in the assy, so you will have to wash it out. I did this in the thread above, so please it first and take it as a warning.
Bottom line though, you have to find out how the water is getting into the headlight assy. Until then, you will always have water in there.
Has this been done and is there a how to?? 
