The 2 buoy, a lighted red tower, flashing 2.5 seconds marks the east side of the channel just above the GW Bridge at W 181 Street.
If you click on the thumbnail and look carefully below a branch, in a straight line below the bow of the light fuel barge seen here on a January afternoon with my low res waterproof camera, you' ll see the snow and ice encrusted 2 buoy doing icebreaker duty as the river shoves those floes down river at 3.3 knots (not the 2.0 predicted peak in Eldridge's Pilot Guide) I know because in the still waters of the Morris Canal my North River 2 does 5.2 kts. And I have spent many hours making 1.9 kts. northbound against the ebb tide.
The other two shots are the Katherine Walker (CG buoy tender) setting the newly painted replacement buoy, and backing away using both bow and stern thrusters.