What does a "flashing white light" on a buoy most commonly indicate?

A "flashing white light" on a buoy most commonly indicates a safe water mark. These marks serve to denote areas of safe water, and they are typically positioned to indicate that there is navigable water in the vicinity. The nature of the flashing white light provides visibility and an indication to vessels that they can safely navigate around it without encountering hazards.

Safe water marks are crucial for guiding boats through channels and routes that might otherwise present dangers, such as shallow waters or rocks. The consistency of the safe water mark's characteristics, including the light pattern, helps mariners to clearly identify the buoy's purpose even in varying visibility conditions, such as fog or at night.

In the context of the IALA Maritime Buoyage System, safe water marks are fundamental for navigation, reflecting the importance of buoys in ensuring maritime safety.