Want this question answered?
It is the "Masters Salute", a salute to the Master of another vessel.
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.
Three short blasts tell other boaters, “I am operating astern propulsion.” For some vessels, this tells other boaters, “I am backing up.”
3 short blasts
You need to transmit the Morse letter D (-..) with either a fog horn or hitting a bell every 2 minutes. Long blasts need to be 3 times as long as short blasts. The space between blasts is as long as the duration of a short blast. So the sequence goes like this: Blow the horn or hit the bell for 6 seconds, wait for 2, hit it for 2 seconds, wait for 2 seconds, and hit it again for 2 seconds.
3
3 blasts on the horn says you are going astern
3 short blasts
3 short blasts
3 short blasts
3 short blasts
3 short blasts