The beach has a high gay population. It is the ONLY nude beach for 100's of kilometre's around. I enjoy tanning and having the breeze hit me nude. I'm locked in doors at work and school all day.
What am I to do?
You are to do what women have been doing since the dawn of time, when approached by an aggressive male that they're not interested in. Welcome to their world.
If you are hanging out on a gay beach, it should be no surprise that someone might approach you, thinking you are gay, or or at least interested in other gay men. It's an understandable confusion on their part. They don't know you're str8 and thus should automatically stay away (even though most WILL stay away anyway -- depending on the cruisness of your beach -- nude beaches are usually jsut that, nude beaches, not cruising spots).
Just like str8 men, some gay men or more forward/aggressive than others. Some assume anyone and everyone will be attracted to them if they just "show off". Sounds like you have found/experienced that.
For me, to ward off such unwelcome advances on the nude beach, I simply temporarily cover my penis with a towel or whatever is handy, give "the look," and that pretty much takes care of it. They get the message 99% of the time.