Your vessel is backing out of a slip in a harbor. Visibility is restricted. Which signal are you required to sound?

When a vessel is backing out of a slip in restricted visibility, the appropriate signal to sound is one prolonged blast. This signal is intended to communicate your intention to other vessels in the vicinity, indicating that you are maneuvering in a way that could affect the navigation of others. By using a prolonged blast, which lasts about four to six seconds, you ensure that other mariners are aware of your actions and can take necessary precautions.

The context of this situation reflects the importance of maintaining safety while operating in restricted visibility conditions. The prolonged blast serves as a crucial warning to nearby vessels that you are in motion and potentially altering your course or position.

In this scenario, other options such as two short blasts and five short and rapid blasts do not apply to the situation of backing out of a slip. Two short blasts signify a turn to starboard when under power, while five short blasts are used as a signal that indicates confusion or that the operator does not understand intentions. Therefore, the one prolonged blast is the proper and required signal in this context for a vessel backing out of a slip when visibility is limited.