There have been several occasions where I was caught not only naked, but in the middle of a very hot fuck.
In the first instance I was at a conference at a Disney owned hotel with intense security, where at 2am encountered a very built, hairy and handsome guy younger than myself walking near the pool. Absolutely no one around, we thought, so not long after our mutually magnetic encounter I had his legs in the air and was slamming his chute, near the exit from the central mountain feature's tunnel with him laid back on a pooldeck lounge chair. Apparently, the lady had a bad experience with her mate and exited her hotel room to clear her mind and saw us in the heat of intense passion. Buck naked, the both of us. She gasped, and proclaimed "oh never mind me!" as she scurried away. I told him we'd better move. We went over a boundary and I strapped him to a palm tree at his request, again hearing voices, but this time with flashlights. We were ready, slamming up our pants and exiting to the walkway. Security was really all too anxious to demo their badass, but on learning I was a guest backed immediately off. It was actually quite stimulating.
The next time, my partner and I got the urge, backing my Super Beetle against a dead end road guard rail, the forest and a river behind. He had his feet on the rear bumper, braced against the curve of the back window, and my thrusts were bouncing the suspension quite admirably. Suddenly we heard the familiar sound of a bike moving at a good clip and immediately "Wooo-HOOOOOO!!!" rang out in a female party voice. We had parked next to a bike path. We both laughed hard, but did not stop our fun.
The final event was in the middle of absolutely nowhere high in the Italian central alpine mountains, outside the car, standing, pants down and with perfectly synchronized repetition at the height of being lost in sublime thrusts, an old farmer strolls right past from behind us. Tending cows down the hill behind, he was returning to a nearby shed. We joked he'd never be the same, and may have had difficulty not thinking about it the next time he bonked his lady friend. We still laugh about it.
Though initially embarassing and not having wanted to subject anyone to what they did not want to see, it's now fun to recall and relate the experience, as I'm sure the three of them have done many tines themselves (perhaps short of the Italian farmer who will probably keep that one under wraps) .