What sound signal should an anchored vessel longer than 100 meters use to indicate its presence?

An anchored vessel longer than 100 meters is required to use specific sound signals to indicate its presence, ensuring nearby vessels are aware of its location, particularly in reduced visibility conditions. The appropriate signal for such vessels is to ring the bell rapidly for 5 seconds at intervals of one minute. This method effectively alerts other vessels to their presence without being overly disruptive.

This sound signal is part of the regulations set forth in the COLREGs, which aim to enhance safety on the water and prevent collisions. The rationale behind this specific signal is that it is both effective and appropriate for the size of the vessel. The ringing of the bell serves as a clear and distinctive sound that can be easily heard over distances.

The other options presented do not align with the standard requirements for anchored vessels as defined by the regulations. For instance, three bell claps followed by a whistle may not be recognized as the specific signal required for a vessel of this size, and using an SOS signal or flames/gunfire is not in accordance with the standard signaling methods for anchored vessels. These alternatives either are inappropriate for notifying nearby vessels of the boat’s position or are reserved for emergency situations, rather than routine signaling.