You have had words with the skipper, might be worth a chat with the sailing club to ask if kinda stuff is expected in "fun" reaces; it might be that this skipper is known for it and they just ignore him. If it's a known problem, they may be dealing with it in a way you are not aware.

If not a known problem, a chat with the commadore may mean the skipper gets a chat "from someone with big boots" and he then understands it is not appropiate to miss marks. If no joy next time; simply get witnesses and then suggest to the skipper that it's not on; if not joy; PROTEST!