A. Three prolonged blast of the ships whistle or general alarm at an interval of three means a man overboard. This is dismissed by three short whistle blast.
B. Three Short blast can also be Rule 34 "Maneuvering and Warning Signals."
Three short blast means "I am operating astern propulsion."
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.
One short blast of a boats horn can mean a couple of things.Horns are used to communicate with other boats to avoid collisions.If you are overtaking a boat from the rear, one short blast will let the other boat know that you are going to pass them on the starboard side, two blasts indicate passing on the port side. The other boat should return your one blast, or two blasts, to let you know that they are aware of you and acknowledge your intentions.If you are heading straight towards another vessel, one blast will indicate you intentions of passing port to port. If you pass starboard to starboard then two blasts are required. The last situation is if you are going to be crossing in front of another boat. Remember, the boat coming from the right has the right of way. Giving one blast lets the boat to your right know that you see them and are going to give way to them, again all these signals should be acknowledged by the other vessel. If you do not receive a return signal, assume they are either drunk or do not see you. These rules are for inland waters, such as lakes rivers, bays, harbors and the like. Different rules may apply when you are on the high seas.One short blast of a boat horn means that the boat is altering course in a starboard direction. One long blast means that the boat is nearing a bend and cannot see oncoming boats.
Two short horn blast from a vessel means that she is turning port and one short horn blast that she is turning starboard
on short blast
Two short blasts mean that one intends to overtake the other on the port side. One short blast, on the other hand, means that one intends to overtake the other on the starboard side.
It is called a short salute and is how ships greet each other.
Runaway ship
Vessel operators can alert the lock attendant of their request to transit through the lock by sounding one prolonged blast followed by one short blast
Rules of the Road. Rule 32. Sound & light Signals Definitions (B) The Term "short blast" means a blast about one seconds duration. (c) The Term "prolonged blast" means a blast of four to six seconds duration. Rule 34 Maneuvering and Warning Signals International. (a)One Short blast means "I am altering my course to starboard" (right) Inland. (a) One Short blast means "I intend to leave you on port side" (left)
You could 'toot' your horn...
Toot
toot