According to the Navigation Rules, which factor must be considered in determining a safe speed?

Determining a safe speed while boating involves evaluating several critical factors, one of which is the state of visibility. This encompasses how well a boater can see other vessels, navigational aids, and potential hazards. Poor visibility due to fog, rain, or other conditions necessitates a reduction in speed to provide adequate reaction time and maneuverability, thereby ensuring the safety of all water users.

Other factors, while relevant to overall navigational safety, do not directly influence speed in the same compelling way. For instance, the time of day and the number of boats on the water can affect a boater's awareness of their surroundings and the likelihood of encountering other vessels, but they do not inherently dictate a need for increased caution or a speed adjustment. Similarly, the size of the boat can influence its handling and ability to navigate through various conditions but is not a primary consideration in relation to speed compared to visibility.