When approaching a buoy with a number 4 and a flashing red light while traveling upstream, keep the buoy on your port (left) side.
When traveling upstream on a river and encountering a buoy with a number 4 and a flashing red light, you should keep the buoy on your port (left) side. In maritime navigation, red buoys are known as nun buoys and they mark the left side of the channel when entering from seaward. Remembering the saying about port wine being red can help recall this knowledge.
https://brainly.com/question/37692391