I do quite a bit of water and land based surf photography. A lot of the good non pros don't have many shots of themselves. If your shots are good and you print on good media they are often cool on paying to cover costs, if you are shooting grommets then encourage them and give a few shots away , do a round of shooting at the local kids comps blow up and print good shots as prizes, get to know the parents they love to buy photos of their kids and so you don't get a reputation as a pervert.
Just don't become a navigation hazard in the line up, all credibility goes out the window when you do that.
If pros are about they often come with a pack of camera crew and they fight as much in the line up as the pros do! They can be a bad mannered lot as their meager money depend on their shots.
A pro alone and in most circumstances asking usually helps unless you are at a secret forbidden line up.
Then you need a secret service hidden camera and a high run away speed.
Good considerate question shows you are thinking, look forward to generating shots like this.
PS remember to duck