What is the purpose of the two prolonged blasts followed by two short blasts signal?

The signal consisting of two prolonged blasts followed by two short blasts is an important recognized sound signal used in maritime communication. This specific sequence serves to convey to other vessels that the signaling vessel intends to overtake another boat on the port side.

In maritime navigation, sound signals are used to ensure safe passage and communication, especially in situations where visibility is limited or where other vessels may not be aware of one another’s intentions. The clear articulation of intentions helps prevent collisions and allows all vessels in the vicinity to understand one another's maneuvers on the water.

The context surrounding other options points to different sound signals. For example, the signal for a vessel safely at anchor is typically a single prolonged blast every few minutes rather than the sequence mentioned. The intention to embark passengers would be signaled through other communication methods, as it does not typically involve a specific sound signal. Finally, while a vessel approaching to moor may use sound signals, they would not be the two prolonged and two short blasts, as that specific signal is distinctly linked to overtaking maneuvers.

Thus, the understanding of this sound signal and its correct application is critical for safe navigation.