What must a vessel do if it cannot accurately determine the windward vessel?

A vessel that cannot accurately determine the windward vessel is required to keep out of the way of the other vessel to prevent potential collisions. This is in line with the COLREGs, which emphasize the importance of avoiding risky situations in situations of uncertainty.

In cases where a vessel is unsure of its surroundings or unable to identify other vessels clearly, taking actions to maintain safety is paramount. Keeping out of the way demonstrates a proactive approach to preventing hazardous encounters on the water. This action aligns with the general principle of giving way to vessels that may pose a threat based on the relative positions and circumstances, particularly when the vessel may be less maneuverable or has limited visibility.

The other options do not align with the COLREGs’ guidelines in such contexts. Not sailing entirely might be impractical and unnecessary if keeping a safe distance from other vessels is enough to ensure safety. Proceeding as normal without awareness could lead to accidents, and signaling when unsure of another vessel's position isn't sufficient to mitigate collision risks in the absence of clear identification. Therefore, maintaining the necessary caution and yielding to the other vessel is the best responsible action in such a scenario.