A. Three long 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 (Inland and International) "Maneuvering and Warning Signals."
Three short blast means "I am operating astern propulsion."
it is the same right
Six blasts of a ship's horn does not seem to have a meaning. Five blasts will mean that you are possibly too close to another ship.
One long honk on the horn
Three short blasts tell other boaters, “I am operating astern propulsion.” For some vessels, this tells other boaters, “I am backing up.”
three short blast
gat out of my way
Get The Bleep Out Of The Way.
A warning to other boaters there is danger near by.
A boat is astern propulsion and is in the act of backing up
Passing on your starboard (right) side.
I intend to pass you on my starboard (right) side.
Means it's about to turn to port.