I always used to go to nude beaches all the time. Love the freedom. Sometimes, I'd get hard, no big deal. It went away. Nobody minded, as far as I knew. These were beaches with no kids around, which might have made me feel differently.
Once, south of San Gregorio, I got hard as hell; I was with my future wife. We went to the top of a boulder and fucked like rabbits. Fantastic, sun on my ass.
Later, on Baker Beach in SF, i threw wood when I fell asleep. A guy was crouching down beside me when I awoke. I am 9 x 7, and he really liked what he saw. (I drifted gay after divorce.)
We broke all the rules and went up into the weeds to fuck. He couldn't do much with his mouth, so I fucked him. He loved it balls-deep, which lots of guys don't. I'm mainly a bottom, so he fucked me too. Nice afternoon. I don't think anyone saw us, but I wasn't looking.