<human>: Summarize the given text in a few sentences.

I'm on mobile and don't want to type too much, but here it goes.

Backstory: My girlfriend and I have been dating for 5 months, and things have gotten very serious, to the point where we know we want to marry each other, even though we are young and haven't dated for very long. She has told me that she doesn't want to do anything that would make me uncomfortable and/or see lesser of her, and she won't if I don't want her to. But I don't want to be a controlling boyfriend.

She thinks it would be fun to go skinny dipping, and doesn't see a problem in other guys seeing her naked, that it would be fine. Its "just skinny dipping". But I don't like the idea, men are visual creatures, and I wouldn't want other guys to see her naked. Its also why I don't want to go with her, even if there were no other guys, I don't want to put myself in a situation where I might have sexual thoughts about another girl. I can control my thoughts, but why set myself up for that. And she thinks that its fine, its just having fun and not sexual. I asked her if she would be fine with some of my friends girlfriends to see me naked, and she said yeah, "cus its different for guys and girls". So I think she does have an understanding that guys are visual creatures. I just feel like it would make seeing her naked less special, like the requirement for that would be lowered from significant other to someone she's fine going skinny dipping with.
<bot>: Just the thought of other guys seeing her naked makes me feel very uncomfortable, I'm not sure what to do. Advice?