What signal is used for approaching a bend or narrow channel?

The signal used for approaching a bend or narrow channel is a prolonged blast. This sound signal serves as a warning to nearby vessels of your presence and intentions, particularly in situations where visibility may be compromised or where vessels may not be able to see each other directly. The prolonged blast, which lasts about four to six seconds, communicates your approach and encourages others to remain vigilant and aware of potential meetings in confined or restricted waterways.

Understanding the context for signal use is crucial in maintaining safety on the water. The other options represent different sound signals that have specific meanings. For example, two short blasts followed by one long typically indicate a vessel's intention to overtake another vessel on its starboard side, while three prolonged blasts signal a vessel operating in the fog indicating its position. Similarly, four short blasts relate to a vessel indicating a crossing or a change in direction. Each sound signal has its distinct purpose, reinforcing the importance of using the correct signal in maritime communication to avoid accidents and ensure navigational safety.