Why did a naked young man ask a girl on the beach to touch his male genitals?

There could be various reasons behind such a behavior, but without specific context, it's difficult to determine the exact motivation. It may stem from misguided attempts at flirting, a lack of boundaries, or other personal issues. It's important to remember that such behavior is inappropriate and can be alarming or uncomfortable for others. If you encounter a situation like this, it's advisable to prioritize safety and report the behavior to authorities if necessary.