tell the guy that you are fully insured for your activity and it is probably best that they sort this issue out bearing in mind the 'large' claim that he is making, and give him your insurance details , then ask him for his insurance details that cover him for what he was doing - that shuts them up!

The rights of way rules try to give right of way to the least manouverable/slowest boat. so you were probably in the wrong - but never admit it.