What is the manoeuvring signal to indicate 'I am operating astern propulsion'?

The correct signal to indicate "I am operating astern propulsion" is three short blasts of the whistle. This signal is part of the International Regulations for Preventing Collisions at Sea (COLREGs), specifically pertaining to the sound signals that vessels must use to communicate their actions and maneuvers to other vessels in the vicinity.

When a vessel makes three short blasts, it communicates its intention to operate in reverse or astern. This is crucial for ensuring safety at sea, as it informs other mariners of the vessel's current maneuvering status, allowing them to take appropriate action to prevent collisions. The clarity of sound signals is vital in ensuring all vessels are aware of each other’s intentions, especially in busy or confined waters.

The other signals mentioned have different meanings. For example, one prolonged blast typically serves as a warning signal or indicates that the vessel is about to leave a berth. Additionally, two short blasts indicate that the vessel is altering its course to starboard, and one short blast signifies an intention to alter course to port. Understanding these distinctions is essential for effective navigation and communication at sea.