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3 blasts on the horn says you are going astern
A boat is astern propulsion and is in the act of backing up
When backing up a boat, it's recommended to sound two short blasts of the horn to signal your intention to reverse. This communicates to others in the vicinity that you are maneuvering backward. Always ensure that you're aware of your surroundings and any other vessels in the area while backing up.
Three short blasts tell other boaters, “I am operating astern propulsion.” For some vessels, this tells other boaters, “I am backing up.”
One long honk on the horn
three short blast
Three short blasts means you are operating in reverse. One prolonged blast followed by 3 short blasts means boat under tow in redcued visibility conditions.
Passing on your starboard (right) side.
A vessel that is backing up typically uses a series of short blasts on its horn to alert other boats of its intention to maneuver in reverse. This sound signal consists of three short blasts, which indicate that the vessel is preparing to move backward. This is part of the International Regulations for Preventing Collisions at Sea (COLREGs) to ensure safety on the water.
When two boats approach each other, they use horn blasts to signal the other about their intentions when it comes to moving to avoid collision. 5 short blasts indicates that the signaling boat is unsure about what the other boat is doing.
Means it's about to turn to port.
Five short horn blasts from another boat on the water usually means danger. It could mean they have doubt in the message they had received from you, whether they did not hear it or did not understand. It can also be used to signal that the boat driver is confused about who has the right away. It is a signal to alert another vessel that you are unsure of its intentions, or doubt whether you are taking enough action to avoid a collision.