When must vessels sound their fog signals?

Vessels must sound their fog signals when visibility is restricted due to fog or similar conditions to ensure safety on the water. In low visibility situations, sound signals serve as a means of communication between vessels, helping to alert others to their presence and position. This is crucial in preventing collisions, as it becomes difficult to see other vessels, navigation markers, or land features.

The regulations specify that sound signals should be used in conditions where visibility is notably compromised, such as in fog, rain, or snow. This requirement is part of the navigation rules aimed at enhancing safety and ensuring that all vessels are aware of each other's locations when visual cues are limited.

In contrast, sounding a fog signal while in a port, when visibility is clear, or merely near other vessels does not align with the defined conditions for using these signals. The purpose of the fog signal is specifically to address challenges posed by obscured visibility, emphasizing that proper use is essential for maintaining safe navigation in such situations.