I go to the gay section of my local nude beach ( Gunnison Beach, Sandy Hook NJ) on a regular basis. This is somewhat similar to in all-male spa as far as etiquette is concerned. All of the comments above are useful and are pretty much the same here.
If you walk past somebody that is eyeing you or you eye somebody and they smile back at you that is a good time to start some small talk just like any other beach or bar situation. If he is naked and starts to get a bit erect maybe swing your small talk to something more sexual such as remarking how nice his cock is or I love the smooth look around your cock and balls. Likewise if you start to get erect and he slides her hand over onto your thigh maybe help it along or move your body to let him know that you’re interested. Never force yourself on to somebody or if you do and he shakes his head stop what you’re doing and politely excuse yourself. Likewise if for some reason some guys do prefer to leave a small Speedo or short shorts on. Again go by the same as above and you’ll go wrong.
The best one is in this is happened to me where I saw a guy walking out into the water with a full-fledged hard on, he walked up to me started some small talk while rubbing the head of his cock on me. Eventually he turned my back to the beach dropped to his knees and started sucking my cock.
Bottom line is always be respectful of yourself and other people’s wishes. Never force yourself upon anybody but certainly know that everybody is there to enjoy themselves and the more the merrier.