The steamroom where I work out (in NYC) has quite a little jackoff scene. One needs to watch the door, but there've been as many as 5 people goin' at it in there, solo and/or in combination. And again, out at the end of another area nude beach (not Fire island) one often sees, how shall I say, mutual sharing of a secret handshake. It's mostly guys but also women & men do one another out there. Sometimes there's a nice little audience. And, um, see this story, which is, of course, all fantasy uhhunh ;-)
http://www.lpsg.org/fictitious-stories/40750-a-true-story.html
Lemme say, though, the risk gets greater and greater, I think, because cellphones make it easy to report someone. Most LE takes this sort of thing very seriously and, if caught, you can and probably would be prosecuted for lewdness. Depending on where you live, there's a good chance it will be reported in local newspapers and, well, it could be extremely embarassing, or worse -- so, okay, obviously, "discretion is advised."