"katysails" answered:
MC asked: what would you do?

I would have said something like "Excuse me, but it is illegal to pump
your sewage here. If you don't stop immediately, I will repoirt you to
the nearest authoity" Then I would plyg the holes made in my boat and
go report the a-hole.

I'll essentially ditto Katy. Tell him to stop. Stay and watch. If he
does, ok. If not, report him.

Frank