Hazardous areas are generally marked by Cardinal Marks, of which there are 4 distinct types, each representing the cardinal points of the compass (north, east, south and west). Northerly marks show that there is clear water to the north; south to the south and so on.

Each type of cardinal mark can be disinguished by colour, light sequence or the shape of the topmark.

• Top mark shape

  
  On top of each cardinal mark are two black cones. Depending on the type, the cones point in different directions.
  
  North cardinals have two cones pointing upwards, south - two townwards. East appears to have two cones pointing away from each other and westerly cardinal marks have two pointing towards each other.
  
  

• Colour

  
  

  As shown, all cardinals marks are yellow and black. The banding of the buoys depends on its nature. An easy way to remember the colour pattern is to visualise which way each cone on the top mark is pointing. The black bands appear in these directions.
  
  Example - On a westerly cardinal the two cones point inwards together, so the black band is in the middle, whereas an easterly mark shows two cones pointing away from each other, so the black bands are on top and bottom.

• Light Characteristics

  In general:

  • North Cardinals flash a continuous Quick or Very Quick white flash (Q / VQ)
    
    
  • East Cardinals flash 3 Quick white every 10s or 3 Very Quick white every 5s(Q(3)10s / VQ(3)5s)
    
    
  • South Cardinals flash 6 Quick and 1 Long white every 15s or 6 Very Quick white and one Long white every 10s (Q(6) LFl 15s / VQ(6) LFl 10s)
    
    
  • West Cardinals flash 9 Quick every 15s or 9 Very Quick white every 10s (Q(9)15s / VQ(9)10s)
    
    
  
  
  
  HANDY HINT Two different characteristics are given for each type of Cardinal mark to enable better identification in areas where there may be confusion. The southerly cardinal's light sequences contain a long flash to distinguish it from the westerly cardinal.
  
  It may also be easier to consider the Cardinal points on a clock face. Eg. East at 3 o'clock = 3 flashes, West at 9 o'clock = 9 flashes etc.

There are two different marks that are used to mark the edge of a channel - Lateral Marks. They are green and red in colour, and the side of the channel on which each is placed depends on the direction of buoyage and the IALA region in which they are found.

In IALA Region A (the UK and most of the world) when entering a port or harbour, the red (port hand) marks are kept to your left, whilst the green starboard-hand marks are left to the right

Bifurcation Marks

Sometimes a channel splits into two, with navigable water in both channels. If this is the case, a Bifurcation mark may be used, to indicate which is the preferred channel to use.

Bifurcation marks are green and red striped, with the colour of the middle stripe being the one indicating to which side the primary channel lies; if the post is primarily green with a red stripe the the middle then the preferred channel is to port, and vice versa if the post is mainly red with a green middle stripe.