A woman goes to the Doctor with bruises on her face. The Doctor asks: "What happened?" 

The woman says: "Doctor, I don't know what to do. Every time my husband comes home drunk, he slaps me around."

"I have a real good cure for that." says the Doctor:

"When your husband comes home drunk, just take a glass of water and start swishing it in your mouth. Just swish and swish but don't swallow it until he goes to bed and is asleep."

Two weeks later the woman comes back to the doctor looking fresh and reborn. The woman says: "Doctor that was a brilliant idea! Every time my husband came home drunk, I swished with water. I swished and swished, and he didn't touch me! How does the water do that?"

The Doctor says: "The water does nothing. It's keeping your mouth shut that does the trick."