i would never accept $ for damage that occured in the water. if ya cant stay away from each other(and we all f around with our buddies gettin too close ) ...then practice. its a part of surfing. he could have just as easily hit the pier if he cant avoid you. now if you lend someone a board and they damaged it then I would certainly hope he/she would chip in on the expence of repairs.....what else ya got?
like someone else says, it depends who's fault it was. If it was your boys fault, then he can deal with it. Just say bro, you dropped in on me, WTF? But, my friend, if you dropped in on him it's your fault and you should be fully responsible to pay for it to get fixed. Also, if you don't know how to fix boards, don't attempt it on your friends board. Pay for a professional to get the job done correctly. it's well worth it. Remember.... there's a big difference between breaking someone's board and putting a ding in it. A ding is a little easier to fix.