Yeah...

If your boat is on a public beach, you really just need to assume the worst and prepare for it as best you can. You don't really have "private property" rights, and even if you do, no one is going to respect them (for a thousand different reasons).

If I had a boat with rudders worth $1000, there is absolutely no way they would be on my boat overnight, unless it was at a regatta with at least 30 others like it (even then, it would have to be a very secluded regatta site, and I'd still think twice about it).

Mike