He probably can’t get it up anyway.
Difficult to tell but she may have a small, thin G string covering and he may as well. I think women are legal to go topless in NYC but I doubt full frontal nudity is legal. It may well be though given the lack of morals in NYC and elsewhere.
One would have to have an exhibitionist mindset to get an erection in public. I have visited nude beaches and that was absolutely the last thing I was worried about, mostly it was the effects of the cold water that bothered me....:)