Manoeuvring and warning signals
Large vessels sound a series of specific signals to indicate their intentions to other vessels in the vicinity. Some of the more common signals are listed below.
|Short blast - about one second duration|
|Prolonged blast - four to six seconds duration|
|I am altering my course to starboard||One short blast on a horn or similar device.|
|I am altering my course to port||Two short blasts on a horn or similar device.|
I am operating astern propulsion |
engines in reverse - vessel slowing down, stopping or intends going astern
|Three short blasts on a horn or similar device.|
|Signal by vessel in doubt as to the intentions of the other vessel||Five short blasts on a horn or similar device.|
|Vessel nearing a blind bend in a channel or river||One long blast on a horn or similar device.|
Diver below flag
The signal flag for the letter 'A' shown below is used internationally to indicate 'I have a diver below - keep well clear at slow speed'.
The flag is coloured white and blue and may be displayed either from a vessel or floating buoy. It is an offence in South Australia to exceed four knots within 50 metres of a vessel or buoy displaying this flag.