My wife and I might be considered “light” exhibitionists.
The risk of being seen is quite erotic.
Not sure how we’d feel about someone actually watching but the thrill of discreet public sex is exhilarating.
My wife and I have had sex in playgrounds (after hours of course), sex on hotel balconies, foreplay under streetlamps, sex on patios, sex in lifeguard stand, sex on beach with walking path nearby, sex on hood of parked car, oral in hotel elevator and hallway. Most always after a few drinks to loosen the inhibitions.
It’s the risk of being caught that is exciting, but don’t think we would be able to perform knowingly in front of someone else.