What sound signal indicates a vessel is in astern propulsion?

The signal that indicates a vessel is in astern propulsion consists of three short blasts. This sound signal is standardized under the International Regulations for Preventing Collisions at Sea (COLREGs) to ensure clear communication between vessels regarding their maneuvers.

When a vessel sounds three short blasts, it communicates to other vessels that it is moving backward or reversing. This is particularly important in busy waterways where clarity about a vessel's actions can help prevent collisions and ensure safe navigation. The use of this specific sound signal is designed to be universally understood by mariners, which enhances safety at sea by reducing confusion.

Understanding these signals is crucial for both operational navigation and responding effectively to a vessel in various situations, including those involving mooring or maneuvering in tight spaces.