What does the signal "_ . _ ." signify in international waters?

The signal "_ . _ ." represents a Morse code signal for "I am operating astern propulsion." It is primarily used in maritime communication to indicate that a vessel is moving backward, or stern-first. This is crucial for ensuring that other vessels in the surrounding area are aware of the maneuvering of a ship that is not moving in its usual forward direction.

Understanding this signal is important for maintaining safe navigation and avoiding collisions in international waters. Recognizing the intention of a vessel that is operating on astern propulsion helps other vessels assess the best course of action to avoid any potential hazards or misunderstandings. This signal is particularly relevant in congested or navigationally challenging areas where multiple vessels are operating in close proximity.