First: Region A or Region B?
The world is split into two IALA regions with opposite lateral-mark colours:
- Region A — most of the world (Europe, Africa, Australia, most of Asia, Gulf states). Entering a channel from seaward: red on port, green on starboard.
- Region B — Americas, Japan, Korea, Philippines. Reversed: green on port, red on starboard.
For UK/RYA exams: assume Region A unless told otherwise. The mnemonic for Region B is “Red Right Returning” — which is a US Coast Guard saying. When you cross the Atlantic to the Caribbean, the buoyage flips.
Lateral marks — the channel edges
Lateral marks define the sides of a channel. Region A:
Port-hand mark
- Colour: Red
- Shape (buoy): Can (cylinder)
- Top mark: Red can
- Light: Red, any rhythm except those reserved for other marks
Starboard-hand mark
- Colour: Green
- Shape (buoy): Conical (cone, pointed up)
- Top mark: Green cone, point up
- Light: Green, any rhythm except those reserved
Memory aid: “Can on the Coast” — a can-shaped (cylindrical) buoy is on the port side (the side closer to coast when entering port). The conical pointed buoy is on the starboard side.
Cardinal marks — the killer topic
Cardinal marks indicate the safe side of a hazard. A North Cardinal says: pass to the north of me. The mark is on the other side of the danger from you. Four cardinals = four directions.
The top-mark trick (this is the whole exam)
Every cardinal mark has two black cone top marks. The way the cones point tells you which cardinal it is — and the cones point towards the colour black on the mark itself:
Top-mark memory aid:point the cones in the direction of the cardinal's name on a clock face.
- North — both cones point up (12 o'clock)
- East — point apart, like 3 o'clock arms
- South — both point down (6 o'clock)
- West — point together, like 9 o'clock arms
Light rhythm memory aid: count the flashes like a clock face.
- North — 12 o'clock — continuous (no break)
- East — 3 o'clock — 3 flashes
- South — 6 o'clock — 6 flashes plus a long flash to show you have just passed the bottom of the clock
- West — 9 o'clock — 9 flashes
The other four mark types
Isolated Danger Mark — “black with a red belt”
Black body with one or more horizontal red bands. Two black spheres as a top mark. Light: white, group of 2 flashes. Marks an isolated hazard with navigable water all around it — pass on any side, but not over the top.
Safe Water Mark — “red and white candy stripes”
Red and white vertical stripes. Single red sphere as a top mark. Light: white, isophase, occulting, or one long flash every 10s. Means safe water all around — usually marks the centre of a channel or a landfall buoy. The shape and stripes are deliberately distinct from anything else so you cannot confuse it.
Special Mark — “all yellow, no warning”
All yellow. Top mark: yellow X (St Andrew's cross). Light: yellow, any rhythm not used by white lights. Indicates a special feature — water-skiing area, pipeline, military exercise area, ODAS buoy. Not a navigational warning; chart it from the chart symbol, not the buoy itself.
Emergency Wreck Marking Buoy — “blue and yellow with a cross”
Vertical blue and yellow stripes. Yellow cross as a top mark. Light: blue and yellow alternating. Used for new wrecks until permanent marks can be established. Recent addition (post-2006) to the IALA system.
The four exam question patterns
Pattern 1: identify the mark from a description
“You see a buoy with black-yellow-black stripes and two top marks pointing apart. What is it?” Answer: East Cardinal — pass east of it. The top-mark direction + colour pattern is the telltale.
Pattern 2: identify the mark from its light
“Q(9) every 15 seconds.” Count: 9 flashes = West Cardinal. The light alone is enough to identify cardinals in the dark.
Pattern 3: which side to pass
“The chart shows a North Cardinal off a rocky promontory. What side do you pass?” Answer: pass to the north of it (between the cardinal and the open sea, away from the rocks).
Pattern 4: chart-symbol matching
You are shown four chart symbols and asked which corresponds to a described mark. The shorthand: red diamond = port-hand, green triangle = starboard-hand, BYB = East Cardinal symbol on chart, etc. Practice on real charts — the symbols are tiny and easy to mis-read.
Drill it
Mnemonics get you through the first reading. Reflexive recognition comes from repetition. Use the quizzes and the full reference page: