There's a bit of drain I fish where a farmer's put no fishing for 50yds signs up. Not because he has any jurisdiction over the bank, but because he doesn't like looking out of his living room window and seeing anglers. After a number of differences of opinion, he went and got a flock (?) of geese, which are quite the most aggressive birds around. Stay off his bit of bank, nil problemo. Sneak it up with a rod, lop a bait in the forbidden zone and they're straight after you.