7586 you should note that unless you are licensed as a "shore" station you may not communicate by vhf marine radio with a vessel on water unless it is an emergency. You are not required to have a license to communicate from a vessel on the water to another on water vessel. Radios on shore are supposed to have a license.
The following marine vhf channels are the most commonly used on the Hudson. Some are required to be monitored dependent upon the class of the vessel.
Channel 12 - VTS control south of the GW Bridge. Commercial vessels must monitor.
Channel 13 - Commercial Vessels north of the GW Bridge Commercial vessels must monitor.
Channel 16 - All VHF equipped vessels must monitor.
Channel 17 - local law enforcement vessels only
Channel 21 A - USCG Only
Channel 22 A - USCG safety broadcasts
Just a note that since the Project 21 system has been implemented in District 1 the location of vessels transmitting 1 watt and up have become much easier to locate. Lower powers are also easier to track now. If you are interested in the system you can also refer to the USCG web site.
For a complete official listing of the marine VHF Channels please refer to :
http://www.navcen.uscg.gov/marcomms/vhf.htm