What signals must a sailing vessel use when overtaking another vessel?

When a sailing vessel is overtaking another vessel, the appropriate sound signals are two prolonged blasts followed by two short blasts. This specific sequence is utilized to communicate the vessel's intent to overtake and is aligned with the International Regulations for Preventing Collisions at Sea (COLREGs).

The two prolonged blasts indicate that the overtaking vessel intends to pass. The addition of two short blasts further clarifies the action being taken, signaling the intention to overtake the other vessel rather than simply maintaining course. This is essential for safety, as it helps to prevent misunderstandings between vessels operating in proximity to one another.

Using other signals, such as one prolonged blast or five short blasts, does not convey the specific intention to overtake and may lead to confusion or unsafe navigation practices. Therefore, it's critical for vessels to use the correct signal to ensure clear communication while maneuvering on the water.