What if you are traveling upstream on a river at dusk you see a buoy with the number four in a flashing red light what should you do?

If you see a buoy with the number four and a flashing red light while traveling upstream, you should be cautious as this typically indicates a hazard or a warning. Flashing red lights often signal upcoming dangers, such as shallow waters, obstacles, or other navigational hazards. It's essential to reduce your speed, maintain a lookout for potential dangers, and prepare to navigate safely around the area. Always consult your local navigation charts for specific meanings related to buoy markings in that region.