A warning to other boaters there is danger near by.
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
gat out of my way
it is the same right
Get The Bleep Out Of The Way.
Passing on your starboard (right) side.
I intend to pass you on my starboard (right) side.
Means it's about to turn to port.
It is the "Masters Salute", a salute to the Master of another vessel.
Three short blasts tell other boaters, “I am operating astern propulsion.” For some vessels, this tells other boaters, “I am backing up.”
They intend to pass starboard side to starboard side.
Passing on your right side.Signals are (number of blasts):1. Passing you on your left (port) side2. Passing you on your right (starboard) side3. I am moving backwards (astern)4. Danger, don't do that (answer to the other three if dangerous)One short blast means 'I am changing course to starboard.'Two short blasts mean 'I am changing course to port.'Three short blasts mean 'I am operating astern.'Two prolonged blasts followed by one short blast to mean 'I intend to overtake you on your starboard side';Two prolonged blasts followed by two short blasts to mean 'I intend to over-take you on your port side.'A long blast every two minutes is used when operating in fog.