At the age of 5 my daughter discouraged a would-be exhibitionist (and God only knows what else he would have been) by telling him that wasn't his sneaky snake, it was his penis. She wouldn't have known that if she hadn't regularly showered with her Daddy. At an appropriate age, she established her own boundaries for privacy. She was never upset by this experience until she was older and realized what had actually happened. At that point, she decided she would be open with her children concerning their bodies, as her parents had been.