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

The signal used for approaching a bend or narrow channel is one prolonged blast. This signal is intended to inform other vessels of your presence and intention to navigate through an area where visibility may be limited or where it might be difficult to ascertain the position of other vessels. By using one prolonged blast, you are effectively communicating your approach to any vessels that may be in the vicinity, thus enhancing safety and reducing the risk of collision in areas with restricted visibility. This practice aligns with the rules concerning sound signals in tight navigational scenarios, allowing vessels to be aware of each other’s movements.

The other options represent different intents and situations within the navigation rules, making them unsuitable for the specific scenario of signaling an approach to a bend or narrow channel. Thus, the choice of one prolonged blast serves a critical safety function in maritime navigation.