Higgs, almost all local Bar Assoc. (the lawyer kind, not the fun kind) have a program whereby you can be referred to an attorney who will listen to you describe the situation and then advise you as to you options etc. It's about $35 to $50 for 30 minutes AND of course you should always consult a bloodsucking, I mean an attorney. My lawyers make me say this.
Luckily I'm not a lawsuit magnet anymore, but the system that worked best for me was:
If you do not want to pay him something to go away.
If the first "demand letter" (also known as shaking the tree) is on personal stationary, I'd write back on better stationary. Sometimes they'd write with a crayon on stationary with daisies.
If the first shakedown letter was from an attorney I'd have my attorney respond on better stationary.
In this case I would respond something like:
Dear Mr. Fisherman,
Thank you for your letter of January 22 regarding the damage to our marker bouy, this has removed any uncertainty.
The damage to our property has been estimated at $600 by the adjuster, you'll find our return address on our letter head. Checks may be made payable to: Great White Shark Yacht Club. Thank you for your prompt attention to this matter.
Yours, Vlad the Impaler.
Oh, I almost forgot, your third option is to let your insurance company handle it for you but they will just deny his claim (at least the first time). They may settle but they'll make Mr. Fisherman answer a LOT of questions first and won't admit liability. Neither your club or the insurer wants to become an easy target for other sportsmen.