You personally? Show's I've been to, cops have been called or hired to protect the perimeter from people getting too close, and in the case of water shows... the Coast Guard or police boats enforce the line.
Hi, Hair. I do the Carnation show every year. Small show, not many problems. We do have access to the cops and the firemen, but usually I have to handle it before they show up. (The locals know ALL the shortcuts)