I don't know if its illegal or not to shoot off a boat, but waterfowl hunters sometimes do. I would be concerned especially if they were shooting in the direction of people, using lead shot, in the direction of cottages, etc etc.
The reply from police is common, unfortunately.
My last encounter with a DEC warden was at a local post office when I tried to ask him a question, he was extremely rude. The clay target shooters didn't exercise good judgement. Glad no one was hurt.
The Hermit