There was water with a face in THE ABYSS, but it doesn't match the rest of your description.
Likewise, I think HOLLOW MAN had scenes with Invisible Kevin Bacon in rain or under sprinklers, not sure if there was a scene where he is looking in the mirror and is only visible because of the water on his head though.
Those are the two things that come to mind and they don't sound close to what you're looking for, but maybe it will help.
How old are you? Or, what time frame of movie are we looking at here? If you're older then we can start looking further back. Etc.
I'm 18. I don't remember how old I was when I saw the scene but I'm guessing I wasn't 10 yet.