The legendary one handed gesture should be completely adequate. If the jet boat guy takes umbrage then you will have to deal with it. The last man who frightened me was a Viet Cong.

On the Lewis, some years ago, a jet boat blasted over a fish my partner was fighting. Knocked the fish off, of course. We never saw it again. Anyhow, I employed this tried and true means of communication and the guy turned around and came back. What followed was a long loud conversation that slowly turned into a long meaningful discussion which did not include rolling around on the nearby gravel bar or bleeding. My gesture was rude, certainly, but not nearly so rude as his action and he finally saw the error of his ways. I still see this man on the Lewis and the Cowlitz from time to time and I notice that he is always a carefull, polite jet boat driver.

Finally, throwing rocks, busting caps, and all other such idiocy ain't the answer fellas. Communication is the ONLY alternative. I'm fifty-seven years old and I've got the scars to prove it.