Why buoyage deserves a few minutes of your winter

Every winter, in a shed somewhere near the water, someone is sanding a hatch and someone else is re-reading a pilot book. Both are good habits. But the piece of knowledge that pays back fastest afloat is being able to glance at a mark, know exactly what it is asking you to do, and do it without hesitation. The IALA Maritime Buoyage System, Region A, covers the UK and most of the world's coastlines, and once the logic clicks into place it never really leaves you.

The system exists because a channel is rarely straight, rarely wide and rarely obvious from the bridge of a small boat in a swell. Marks give you a language: colours, shapes, topmarks and lights that repeat the same message in daylight, in fog and at night.

Lateral marks: the red and green workhorses

These are the marks you will meet most often, lining the edges of channels.

• Port hand: red, can-shaped, and passed on your port side when travelling in the direction of buoyage.
• Starboard hand: green, conical, passed on your starboard side in the same direction.

The old comfort is "Is there any red port left?", and in Region A it holds good: entering a harbour from seaward, red stays to port and green to starboard. What catches people out is that the direction of buoyage is not always "inbound" — it can reverse around headlands, in some estuaries and where local rules apply. Look for the magenta arrow on the chart before you assume anything.

Where a channel splits, you will find preferred channel marks banded in red and green horizontally. The topmark and the upper band indicate which side the main channel lies on. These are worth a slow, careful look rather than a guess: if you misread one, you can find yourself in the shallow arm of a junction with very little water to spare.

Cardinal marks: the compass in a buoy

Cardinal marks do a different job entirely. They do not mark a channel edge; they tell you where the safe water lies relative to the mark itself — north, east, south or west of it. They are black and yellow, with distinctive cone topmarks, and they are the marks that reward a proper mnemonic.

• North: two cones pointing up, black above yellow. Light: continuous quick or very quick flashing.
• East: two cones base to base, black above and below yellow. Light: quick flash groups of three.
• South: two cones pointing down, yellow above black. Light: six quick flashes plus a long flash.
• West: two cones point to point, yellow above and below black. Light: nine quick flashes.

Two things make this stick. First, the cones point towards the black: up for north, down for south, apart for east, together for west. Second, the light rhythm follows the clock face — three at three o'clock for east, six at six for south, nine at nine for west, and midnight continuous for north.

Safe water, isolated danger and special marks

Three more families complete the set, and each saves you from a specific mistake.

• Safe water marks are red and white vertically striped, usually with a single red sphere topmark. They mark mid-channel or the seaward end of an approach, and you may pass either side of them.
• Isolated danger marks are black with red horizontal banding and two black spheres as a topmark. They sit on a hazard with safe water all around — excellent to see on a chart, terrible to see close aboard.
• Special marks are yellow, with a yellow X topmark, marking cable areas, racing areas, spoil grounds and limits of various kinds. They are not navigation marks in the channel sense, and should not be treated as such.

Lights, rhythm and reading them at night

At night, buoyage becomes rhythm. A flash is a short burst; occulting is a steady light briefly hidden; isophase spends equal time on and off. Quick and very quick rhythms belong to the cardinals and to a few other marks with a message you need in a hurry.

Note the character and period of every mark on your passage plan, and write it down. "Fl(4) 10s" tells you more at two in the morning than a vague memory of a green thing near the harbour wall. Leading lights, sectored lights and transits are worth looking up in the almanac too — a transit is often the most accurate position line you will get all night.

Practical habits that keep you out of trouble

Buoyage is a system that assumes things go wrong now and then. A mark can be off station after a winter gale, its light extinguished, or its topmark missing. It may be a racing mark, a private one, or simply much smaller than you expected.

• Keep a laminated buoyage card to hand in the chart table, and a flask of coffee beside it.
• Note the direction of buoyage for the day's passage, and sketch the three or four critical marks in your notebook.
• Run the depth sounder continuously when close inshore; it is the final arbiter of whether a mark means what you think it means.
• Get the torch out at dusk, not when you need it, and use red light to protect your night vision.
• Keep your own navigation lights clean, working and properly rated — spare bulbs and a charged battery are part of the same seamanship as knowing a cardinal from a can.

Good pilotage is not about memorising rules; it is about building enough familiarity that the water starts to read like a sentence. Give it a season and you will find yourself calling the marks aloud without thinking, which is precisely when the system is doing its job.