I use the loud radio tactic in the summertime when people are making passes too close to my long lines out the back of the boat. I fish open water and set my iPilot to record a trolling track and keep a GPS heading, so when some idiot veers into my trolling path intentionally I crank up the NPR and idle the old 2stroke outboard to scare away the perpetrator. It does nothing to the fish and the usual group of old timers out there with me every week get a kick out of it to boot. If people try to cut behind the boat when I clearly have line trailing behind me I switch to braid so that I don't lose any of my $6 lures when they cross my lines. I go out expecting someone to be stupid these days, common sense has become very uncommon.