Cardinals and dangers

Lateral marks say “the channel is here”. Cardinal markscardinal marksBlack-and-yellow marks naming the safe side by compass: pass north of a north cardinal.full glossary → say “the danger is there” — and they name the safe side by compass point. A north cardinal stands north of the danger: pass north of it. South, east and west cardinals work the same way. They are pillar buoys in black and yellow, and everything about them — bands, topmarktopmarkThe shape on top of a buoy (cones, spheres, ✕) that encodes its meaning.full glossary →, light — encodes the same compass point three different ways.

The topmarks are twin black cones. North: both point up. South: both down. East: they point apart (a black diamond-ish “egg” silhouette). West: they point together (a wineglass — W for wineglass and west). The cones literally point at the black band(s): up-pointing cones, black on top; down-pointing, black below; apart, black top and bottom; together, black in the middle.

Four more you must know on sight

Isolated danger: black with one or more broad red bands, two black spheres up top, white light flashing in groups of two — two spheres, two flashes. It sits on a small danger with navigable water all round; give it a sensible berth on either side.

Safe water: red and white vertical stripes, spherical or with a single red sphere topmark, and a gentle white rhythm (isophase, occulting, one long flash every 10 s, or Morse A). It marks open water — landfalls and mid-channel — and is often the first mark you meet arriving from sea.

Special marksspecial marksYellow marks for non-navigational things — check the chart for what.full glossary → are yellow, with a yellow ✕ topmark and yellow light: racing buoys, outfalls, military exercise areas, data buoys. They mark a thing, not a danger or a channel — check the chart for what the thing is.

Emergency wreck mark: equal blue and yellow vertical stripes, a standing upright yellow cross as a topmark, and a light that alternates blue and yellow (Al.Bu.Yu) — a colour pairing used nowhere else, so it cannot be confused with anything. It is laid fast around a NEW danger, usually a fresh wreck not yet on any chart or in the almanac, and stands guard only until the hazard is surveyed and marked the conventional way. Read blue-and-yellow as “brand-new danger here — give it room and expect nothing about it on your chart yet.”