Yeah, happened to me once many years ago.
I went down to OC Maryland with four college friends for the weekend during spring break. We stayed in the Safari Hotel right on the boardwalk, which has large balconies facing the water. The hotel was full of college kids, and there was a party on each balcony, it was awesome. We ended up talking to these five girls from the University of Delaware who were all hot. Well I really hit it off with one of them who was 20 ( I was 21) and we ended up taking a walk on the beach just to get away from the crowd and comotion.
Long story short, we end up having sex on the beach and get busted by a beach cop (now that is a lump in your throat feeling). Neither of us had ID. He gave us a long speech about the rules of the beach and then told us we were lucky that he was in a good mood, he gave us a warning and sent us on our way.
Once we were back on the boardwalk she starts crying, so we sit on a bench and I try to console her. I tell her that if we would have gotten fined I would have paid it for her. Then she drops the bombshell that she's only 15 and still in high school! Her older sister was the only one of he five girls actually in college, the rest were in HS with her. I don't even know what would have happened if the cop had arrested us and took us in.
That was the last "fling" I ever had, from then on I made sure to know who I was banging.