If you encounter this green marker buoy when heading in the upstream direction (returning from sea) how should you proceed?

When encountering a green marker buoy while heading upstream (returning from sea), you should keep the buoy on your starboard (right) side. This indicates that you are in a navigable channel and that the buoy is marking the channel's edge. Make sure to maintain a safe distance from the buoy and follow any applicable navigation rules. Always be vigilant for other vessels and potential hazards in the waterway.