International boating rules

Distress signals
Distress signals must be used only to indicate need of assistance. Misuse of them may put the lives of others at risk and is illegal.

The following signals may be used to indicate distress.
1. Rockets or shells that throw red stars, fired into the air one at a time at short intervals.

2. A signal:
·       made by radiotelegraphy or by any other signalling method consisting of the letters S O S in Morse Code (••• - - - •••)
·       sent by marine radio consisting of the spoken word: mayday.
3. A square flag having above or below it a ball or anything resembling a ball.
4. A rocket parachute flare or a hand-held flare showing a red light.
5. A smoke signal giving off orange-coloured smoke.
6. Slowly and repeatedly raising and lowering arms outstretched to each side.
7. A rectangle of international orange-coloured material with either a:
·       black letter V
·       black square and circle, or
·       dye marker.
Short Blast - about one second duration
Description: hort blast
Prolonged Blast - four to six seconds duration
Description: ong blast
I am altering my course to starboard.
Description: hort blast
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.
Description:,%20travel%20and%20motoring/Marine/MarineSafety%20images/short_blast.jpgDescription:,%20travel%20and%20motoring/Marine/MarineSafety%20images/short_blast.jpgDescription:,%20travel%20and%20motoring/Marine/MarineSafety%20images/short_blast.jpgDescription:,%20travel%20and%20motoring/Marine/MarineSafety%20images/short_blast.jpgDescription:,%20travel%20and%20motoring/Marine/MarineSafety%20images/short_blast.jpgFive short blasts on a horn or similar device.
Vessel nearing a blind bend in a channel or river.
Description: ong blast
One long blast on a horn or similar device.
8. The International signal of distress indicated by N.C.

international distress signal

9. Continuous sounding of any fog-signalling apparatus.

10. Signal transmitted by an Emergency Position Indicating Radio Beacon (EPIRB).

Manoeuvring and warning signs

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. 

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. 

diver below flag

Navigation lights
Vessels underway at night must show navigation lights. Navigation lights indicate the:
  • presence of a vessel
  • approximate direction of travel
  • type of the vessel ie - power-driven or sailing.
Small rowing and sailing boats
Small rowing and sailing boats are the only vessels that don’t need navigation lights when operating at night, but operators of these vessels must instead carry a torch or lantern showing a white light and show it in sufficient time to prevent a collision.
Under 12 metres in length
Vessels under 12 metres in length use the following lights in various combinations, depending on whether the vessel is sail or power-driven, underway or at anchor.
navigation lights

Masthead light
Stern light
All-round light
Angle of visibility 
Range of visibility
(nautical miles)

As with channel and other lateral markers, the green sidelight indicates starboard and red indicates port, when looking in the direction of travel.
Power-driven vessels while underway
 Power-driven vessels while underway must show either:
  • a masthead light, separate or combined sidelights and a sternlight or
  • a white light visible all round and separate or combined sidelights, provided that the all-round white light is positioned so as not to interfere with the operator's vision.
power driven vessels underway

The masthead or all-round white light must be a minimum of one metre above the sidelights.
Sailing vessels while underway
Sailing vessels while underway must show:
  • separate or combined sidelights and a sternlight or
  • a single, tri-colour lantern, fixed to the masthead.
sailing vessels underway
Vessels at anchor: sail or power-driven
Vessels at anchor, either sail or power-driven, must show a single white light visible all round.
vessels at anchor
Dredge signals
Vessels undertaking dredging, diving or underwater operations display either two black diamonds in daylight hours or two green lights at night to indicate the side on which it is safe for other vessels to pass. This is the only time when red and green lights may not indicate a vessel’s direction of travel.

A dredge also displays either two black balls in daylight hours or two red lights at night on the side where dredging is taking place – to indicate where it's unsafe to pass.
dredge at night
dredge by day

Giving way
If you are required to give way to another vessel, take early and positive action so that your intentions are clear. Avoid making a series of small changes in speed or course that may not be apparent to the other vessel.

If another vessel is required to give way to you, maintain your present speed and course unless it is obvious that a collision may occur. In this case stop, slow down or turn away.
Rivers and channels
All vessels – including sail vessels – must always be navigated on the right (starboard) side of a river or channel in the direction of travel.
rivers and channels

Power-driven vessels crossing
If a vessel approaches on your right (starboard) side you must stop, slow down or change course so as to keep out of its way.
If a vessel approaches on your left (port) side, it should give way to you. Maintain your present speed and course unless it appears that a collision may occur.
power driven vessels crossing

Sailing and power-driven vessels crossing
Powered vessels normally give way to sail. However, in harbours and channels where there is restricted room, small sailing vessels must give way to large powered vessels that cannot easily manoeuvre. Similarly, sailing vessels must also give way to other vessels that are restricted in their ability to manoeuvre, including fishing vessels that may have nets or other equipment over the side.
sail and power driven vessels crossing

Power-driven vessels meeting head-on
Each vessel must alter course to the right (starboard) so as to pass on the port side of the other.
power driven vessels head on

Vessels overtaking
An overtaking vessel (including a sailing vessel) may pass on either side if safe, but must keep well clear of the vessel being overtaken.
vessels overtaking

Lateral marks
Lateral Marks are usually positioned to define well-established channels and indicate port and starboard sides of the navigation route into a port.
navigating lateral marks
 lateral marks port
Port mark is coloured red and the basic shape is a can.

lateral mark starboard
Starboard mark is coloured green and the basic shape is conical.

By night a port buoy shows a red light and a starboard buoy shows a green light.

Cardinal marks
A cardinal mark indicates where the safest water may be found and is best used together with a compass. It shows where the mariner can safe pass safely and may:
  • indicate the deepest water in an area
  • show the safest side to pass a danger
  • draw attention to a feature in a channel such as a bend, junction or an end of a shoal.
cardinal marks
Think of a clock face when remembering the lights on cardinal marks.  Three flashes for east, six flashes for south and nine flashes for west.
By day the colour scheme can be remembered by noting that the black segment is positioned where the cones point.
  • North – the top mark points up and black segment is at the top
  • East – the top marks point outward and there are black segments top and bottom
  • South – the top mark points downward and the black segment is at the bottom
  • West – the top marks point inward and the black segment is in the middle.

Top marks

Black double cones, clearly separated.

Colours - black and yellow horizontal bands with the position of the black band or bands relative to the respective cardinal points.

 Description: op mark north
Top mark points up, black band above yellow band.
 Description: op mark east
Top mark points outward, black bands above and below yellow band
 Description: op mark south
Top mark points down, black band below yellow band.
 Description: op mark west
Top mark points inward, black band between yellow bands.

Channel markers

Channel markers indicate the port and starboard limits of a narrow channel that has been dredged in a river or the approaches to a harbour to allow safe passage of large vessels. 

The waters outside the channel may be shallow or conceal rocks and other hazards to navigation. Navigating outside the marked channel could result in a vessel running aground and sustaining serious damage. 

Entrances to harbours or breakwaters may utilise different distinguishing characteristics, for example, white flashing lights. Please seek advice from the local marine authority.

Types of markers

Two types of marker are used to indicate the port and starboard limits and these may be either fixed or floating: see picture.
channel marks
The positioning of the two types of marker is determined by the general direction taken by a vessel when entering a harbour or proceeding upstream. 

Under this convention a vessel entering, for example, the Port Adelaide River would keep the port (red) markers on her port side and the starboard (green) markers on her starboard side. 

When leaving the harbour or proceeding downstream the situation is reversed, meaning that the port markers should now be passed on the vessel’s starboard side and vice-versa.

Isolated danger marks
Isolated danger marks are placed on, or moored above, an isolated danger of minimal area below the water around the mark. The water around the mark is safe to navigate. The colours are red and black horizontal stripes and the mark is, when practicable, also fitted with a black top mark of two vertically aligned spheres.

Isolated danger marks are not always positioned centrally over a danger so to be safe do not pass too close to the mark.
If the mark is lit, the light will be white showing a group of two flashes.  Two white flashes of light = two spheres.

Safe watermarks
Safe water marks show that there is navigable water all around the mark and can be used as a centre line, mid-channel or landfall buoy.
The shape of the buoy is spherical, pillar or spar (a round pole shape) and is coloured with red and white vertical strips. The top mark that's fitted when practicable to pillar and spar buoys, is spherical and red.

If lit, it shows an isophase occulting or single long flashing white light. An isophase is a special class of light which alternates eclipses and flashes of exactly equal duration. The buoy shape is optional but should not be in conflict with the buoy used for a lateral or special mark.
safe water marks

Operators of vessels are cautioned that large commercial vessels may pass close by these marks.

Port closed or channel blocked signal

The port closed or channel blocked signal is used to indicate a thoroughfare to navigation that's blocked. The signal may come from a shore station or from any vessel that's blocking the channel.
 port closed day
The marks are made up of three black shapes in a vertical line. The highest and lowest of these shapes shall be a ball and the middle on a cone with apex upwards.
port closed night

Three all round lights in a line where they can be best seen. The highest and lowest of these lights shall be red and middle light shall be green.

Channel blocked signals are increasingly likely to be seen in the River Murray and lakes as the ongoing effects of low water levels cause restrictions to some areas of water.

Day marks
Day marks are shown by day in all weathers on boats to denote certain situations that may limit the vessel’s ability to respond to other vessels, including when visibility is restricted, and must be recognised by vessel operators.
Vessel is restricted in its ability to manoeuvre

daymark restricted manoeuvring

Black ball, black diamond and black ball.
For example boats engaged in cable laying, replenishment at sea, underwater operation, servicing navigation marks or towing, where towing affects the manoeuvrability.

When at anchor, vessel also shows anchor shape. This signal does not indicate distress or a need for help.
Vessel at anchor
vessel at anchor
One black ball.
Located forward, where best seen.
Not required for boats of less than seven metres. Used when at anchor not in a channel or channel approach, or a usual anchorage.
Vessel under power with sails set
daymark under power with sails
One black cone, point down.
Located forward, where best seen.
Power-driven vessel towing another vessel
daymark powered vessel towing
towing measurement

One black diamond on each vessel where best seen if length of tow exceeds 200 metres. 

Vessel aground
daymark vessel aground
Three black balls.
Located where best seen, but not required for boats of less than 12 metres. This signal does not indicate distress or a need for help. 
Vessel not under command
daymark vessel not under command
Two black balls.
Located where best seen. Not required for boats of less than 12 metres. Indicates an inability to manoeuvre, but does not signal distress or a need for help. 
Boats fishing
daymark fishing vessels
Two black cones.
Indicates trawls, nets or other gear - underway or at anchor, point inwards. If fishing vessel is less than 20 metres, she may instead show a basket. 
Vessel constrained by her draught
daymark vessel constrained by draught
One cylinder.
Located where best seen indicates a power-driven vessel restricted to a narrow channel by her draught and therefore unable to deviate from course. 

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