What is a common signal that indicates another vessel is preparing to overtake your boat?

A single long horn blast is a widely recognized signal that indicates another vessel intends to overtake or pass your boat. This maritime signaling protocol is crucial for safety and communication between vessels, allowing boat operators to be aware of each other's intentions on the water. The use of a long horn blast serves as a clear warning that the other vessel is maneuvering, enabling you to take necessary action—such as maintaining your course or speed—to ensure safe passage.

The other signaling options have different meanings: repeated horn blasts often indicate a warning of some kind or that the vessel is altering its course; flashing lights are typically used in certain situations to signal a distress or emergency; and raising the anchor involves preparing to leave a berth or moored position but does not convey any intention regarding overtaking.