I answered your question on East Coast Scanning this afternoon, but I'll post it here also:
Give Marine 17 156.850 a shot.
During boating emergencies, they will generally switch to Marine 16 156.800 to contact the vessel in distress.
The Rockland Sheriff Marine Unit also operates on the Countywide PD Repeater 154.725 (151.4 PL) to talk with "Headquarters" aka 44-Control.
I have no idea about Westchester.