Note before reading: This is an easy to follow article, that I recommend everyone to read, even if you're just a passenger on your next cruise. Surprise your friends by knowing where the ship will go or act in certain situations.

IALA (International Association of Marine Aids to Navigation and Lighthouse Authorities) ensures the safety navigation of all vessels by estabilishing an universal system of buyoaging on which the seafarers have to act on. These are buoys that can be read by the seafarers by their shape, colour and lights. Each one of these buoys have a special meaning and the ships must follow them. The buoys are typically spotted on the nautical chart but RARELY they can be missing and be visually spotted by the OOW (Officer of the Watch). Unfortunately, this system is split in 2 regions. Region A and B. However, there are little differences between them. They both present 6 types of buoys:

Lateral Marks

Cardinal Marks

Isolated Danger Marks

Safe Water Marks

Special Marks

Emergency Wreck Mark

As most of the world is in IALA Region A (shown on the picture above), this article is focused on that but I will explain the differences to B on the go.

IALA Region A

Port Hand Marks (Cylindrical, Pillar or Spar)

These are the Port Hand Marks for IALA Region A and together with the Starboard Hand Marks they form a passage that guides the ship. They are supposed to be left on the port(left) side of the ship as entering the port or in a passage. The difference is that for IALA Region B these would be green.

They display the cylinder at the top which dictates it should be left at Port.

Night: they display a red light.

Starboard Hand Marks (Cone, Pillar or Spar)

These are the Starboard Hand Marks and together with the Port Hand Marks they form a passage that guides the ship. They are supposed to be left on the Starboard (right) side of the ship as entering port or in a passage. The difference is that for IALA Region B these would be red.

They display the cone pointing up at the top which dictates it should be left at Starboard. Night: they display a green light.

Portside Preferred Channel

These are buoys that are shown in the middle of a Y intersection of a passage. Usually the wider or deeper passage is shown as preferred.

We have to guide ourselves to the colour in the middle and not the overall colour of the buoy.

For region B, the colours are changed between them.

Starboard Preferred Channel

These are buoys that are shown in the middle of a Y intersection of a passage. Usually the wider or deeper passage is shown as preferred.

We have to guide ourselves to the colour in the middle and not the overall colour of the buoy.

For region B, the colours are changed between them.

Cardinal Marks

Cardinal Marks show the safest direction to navigate. So if you come head-on with such a buoy, you should alter your course to the direction it points.

Tip on remembering them: North always points up, South always points down. The space between the two cones for WEST resembles a W and the two cones for EAST resemble an E (shown below)

Night: you would see a white light flashing:

NORTH: nonstop quick flashes

EAST: 3flashes

SOUTH: 6flashes

WEST: 9 flashes

Isolated Danger Marks

An isolated danger has safe navigable water all around but in the position it's placed. As long as you don't go close to it, you're safe. Leave it at a distance

Night: 2 white flashes





Safe Water Marks

As the name says, this indicates that the area you're navigating in has safe waters and you shouldn't worry too much. This is your best friend at sea.

Night: 10 white flashes





Emergency Wreck Marks

An emergency wreck buoy is used to tell you of a new wreck which has not been listed in maritime documents yet.

Night: Light alternating blue to yellow





Special Marks

This buoy marks all kinds of areas designed for special purpouses. For example: water skiing, administrative areas, mooring area, anchorage area, waiting area, marine farms etc.

Night: Yellow





This is all. I hope my explenation has been made as simple as possible. I tried to keep it short and include everything at the same time. However, I should try to get better at writing in general, I feel like my articles could be a lot more smoother.

Until the next article,

Bon voyage.