I've had the same problem with landowners up here in WA. I usually try the courteous approach, but if that doesn't work I usually just tell them to lick my bag and to fell free to call the cops if they want.....Just a little word to the wise, if you're gonna do this (the whole lick my bag thing) make sure that you're in the right first. There are a couple of rivers up here in WA where the landowners really do own the land under the river and all the "High Water Mark" stuff doesn't matter.