Finders Keepers Law in NYS?

Hello guys, recently faced with the same problem but with a,little bit worst scenario . During December’s ice fishing on city owned Water supply reservoir located in Westchester county I found a fishing boat sunk on a bottom of that reservoir. With my friend’s assistance we dragged it to the shore( at least a small piece of a board is now above the water surface). I found it was last registered in 2003( every boat must be registered in DEP) And of course I’d like to claim my finder-keeper right. It should be a small book about HOW MUCH time I spent trying to do that in legit way . NYPD, Attorney General office, NYS Comptroller office, 311, Real Property Bureau, Consumer protection office, Public Advocate of the City of NY, name it. I’ve been completely surprised no one has an answer for me, even Attorney General Office attorney. In fact, America sometimes confuses me ; looks like not everything still regulated and clear. I’ve tried to apply an Admiralty Law but fresh water is not an ocean. Any suggestion ?