Interesting.
I would lean toward someone with some type of issue with you. Maybe you were fishing their spot or doing something that doesn't amount to much to you or most, but to this guy it does - especially if this is the third time trashing your boat.
Maybe ask others on the board to help be on the lookout if they are local. I know if someone was doing this on my dock, I'd help. Talk to everyone on the dock. Explain the damage, explain that if you offended anybody you are willing to talk it out. Nobody likes this type of BS except cowards. Ask for an email from the marina each day after an AM and PM check of the boat. Need to make them accountable and on the lookout as well as have documented cases. This could escalate to damage or worse a sinking. In each case take pictures and notify the police of the activity. You will have a documented record of harassment should it be needed. Who knows, you might have a local police officer that owns a boat and makes it his personal mission. We had one on our dock and he patrolled it nightly.
Maybe put a sign on the boat and ask if the person doing this is targeting the wrong person - heck ask them to meet face to face. If no luck, hang a sign in the cockpit detailing the damage and asking for information. Worth a try. I remember when I was a kid a person in an apartment building was trying to beat be out of the cost of 6 weeks of newspaper deliveries. One note on the doors and elevator describing how a 12 year old kid was getting shafted, the game ended and I got paid. Public embarrassment can work if the guy has even a small conscience.
If you put the effort in and get some help, I'm sure you can get the person identified and caught or at least stopped. Need to determine if there is a pattern (day/time etc) that he likes to do his work. Even if no pattern, you can talk specifics with people on the dock - date/time after each occurrence. If the dewbag is on the dock, he will know you are on the lookout and that enough may get it to stop. One thing for sure, the more people do crap like this, like any crime - the more they get lazy.
Once you get him, then you have a wealth of options - especially if documented. I'm sure once caught, he will roll quickly. I don't know many boat people that would like to be associated with such a person and if in the marina, his reputation would be tarnished and he could be asked to leave by the marina. You may not have to do anything once folks know.
He may have a legit beef over something that you don't understand or know about. He could have you mistaken for someone else. Doing coward acts like this instead of talking to you face to face demonstrates that he is a coward.
Good luck. I'd love to know how this one ends.....
