Buoyage & Navigation Marks
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Buoyage & Navigation Marks

Understand the marks that keep you safe on the water

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The IALA (International Association of Lighthouse Authorities) system defines how buoys and marks are used worldwide. The UK and most of Europe use Region A.

Lateral marks define the sides of a navigable channel. In IALA Region A, the direction of buoyage is the direction a vessel takes when entering a harbour or going upstream.

MarkColourShapeKeep to your...
PortRedCan (flat top)Port (left) when entering harbour
StarboardGreenConical (pointed top)Starboard (right) when entering harbour
Port (Red, Can)
Starboard (Green, Cone)
When entering harbour (following the direction of buoyage): red to port (left), green to starboard (right). When leaving, it reverses.
Fill in the blanks
A port lateral mark is ___ in colour and should be kept to your ___ when entering harbour. A starboard mark is ___ and shaped like a ___.
Green
Left
Red
Cone
Right
Section complete!

Cardinal marks indicate the safe side to pass relative to a hazard. They are named after the compass direction of safe water — pass to the named side of the mark.

All cardinal marks are black and yellow with distinctive double-cone topmarks:

CardinalColour (top to bottom)TopmarkPass to the...
NorthBlack over YellowBoth cones pointing UPNorth of the mark
SouthYellow over BlackBoth cones pointing DOWNSouth of the mark
EastBlack-Yellow-BlackCones base-to-base (diamond shape)East of the mark
WestYellow-Black-YellowCones point-to-point (hourglass shape)West of the mark
How to remember topmarks: North = points UP (like an arrow pointing north). South = points DOWN. East = base-to-base like an Egg. West = point-to-point like a Wine glass.

Cardinal light patterns follow a clock-face memory aid:

  • North — Continuous quick or very quick flashing (VQ or Q)
  • East — VQ(3) or Q(3) every 5s/10s — 3 o'clock position
  • South — VQ(6)+LFl or Q(6)+LFl every 10s/15s — 6 o'clock
  • West — VQ(9) or Q(9) every 10s/15s — 9 o'clock
Match the cardinal mark to its topmark
Cardinal
North
South
East
West
Topmark
Drop here
Drop here
Drop here
Drop here
Section complete!

Beyond lateral and cardinal marks, several other buoy types convey specific information:

MarkColourTopmarkMeaning
Isolated DangerBlack with red horizontal band(s)Two black spheresMarks a small, specific hazard with safe water all around
Safe WaterRed and white vertical stripesSingle red sphereSafe water all around — used as fairway/mid-channel marks
Special MarkYellowYellow X-shapeMarks areas like racing zones, cables, pipelines, or military exercise areas
An isolated danger mark sits directly on top of the hazard. You can pass on either side, but do not get too close. Its two black spheres topmark is unique in the system.

Safe water marks are the ones you will see at the entrance to a harbour approach — they tell you that you can safely pass on either side. They are often used as landfall buoys.

Special marks are not primarily for navigation. They mark zones or features. If in doubt about a yellow buoy, check the chart.

Tap each card to reveal the answer
Black body, red band, two black spheres
Isolated Danger Mark — hazard directly beneath, safe water around it
Red & white vertical stripes, red sphere
Safe Water Mark — safe water all around, used as fairway marks
Yellow body, yellow X topmark
Special Mark — marks zones like racing areas, cables, or pipelines
Black over yellow, both cones up
North Cardinal — pass to the north (safe water is north of the mark)
Yellow-Black-Yellow, point-to-point cones
West Cardinal — pass to the west (hourglass topmark)
Red can-shaped buoy
Port Lateral Mark — keep to your left (port) when entering harbour
Tap a card to flip it
All cards revealed!

At night, you cannot see a buoy's colour or shape. Instead, you identify marks by their light pattern (rhythm, colour, and period).

AbbreviationNameDescription
FlFlashingLight is OFF more than ON. Single flash repeated at regular intervals.
QQuick50-60 flashes per minute
VQVery Quick100-120 flashes per minute
OcOccultingLight is ON more than OFF. Steady light with regular periods of darkness.
IsoIsophaseEqual periods of light and dark
LFlLong FlashFlash of 2 seconds or more
FFixedContinuous steady light

Lights on charts are described with a standard notation. For example, Fl(3) G 10s means "3 green flashes every 10 seconds".

Flashing vs Occulting: If the light is mostly dark with brief flashes, it is "flashing". If it is mostly lit with brief dark periods, it is "occulting". Isophase is exactly equal on and off.
Match the abbreviation to its meaning
Abbreviation
Fl
Q
VQ
Oc
Iso
Meaning
Drop here
Drop here
Drop here
Drop here
Drop here
Section complete!

Knowing individual mark types is only useful if you can apply them in real situations. Here are the key scenarios:

Approaching a harbour (following the direction of buoyage):

  • Keep red (port) marks to your left
  • Keep green (starboard) marks to your right
  • Look for a safe water mark (red/white stripes) at the entrance — this confirms you are on the fairway

Leaving a harbour (against the direction of buoyage):

  • Everything reverses: red marks are now on your right, green on your left

Passing a cardinal mark:

  • Identify the topmark first (up, down, diamond, hourglass)
  • Pass on the named side — a North cardinal means safe water is to the north, so pass north of it
  • The hazard is on the opposite side to the named direction

Encountering an isolated danger mark:

  • The hazard is directly below the mark
  • Pass on either side but give it a reasonable berth
When uncertain of the direction of buoyage, check the chart. Arrows on the chart show the conventional direction. In general, direction of buoyage follows the flood tide or goes clockwise around landmasses.
Fill in the blanks
When entering harbour, keep ___ marks to your port side and ___ marks to starboard. A North cardinal mark means safe water is to the ___. An isolated danger mark has ___ as its topmark.
Red
North
Green
Two black spheres
South
Section complete!
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