Harbour Lights Are a Sentence You Can Learn to Read

What follows is the working version of navigation lights and buoyage: the decisions in the order you actually meet them, with the reasoning attached.

The channel has sides

Lateral marks show which side of a channel a vessel should pass, defined relative to entering from seaward. The colour convention is not global: one international region uses red to port on entry and the other uses the opposite arrangement. That is why a chart states which region it is in, and why it is a genuine hazard for someone assuming a single standard.

Buoys are also shaped: can-shaped and conical forms carry the same information in daylight when colour is uncertain. From ashore, the two lines of coloured lights running out from an entrance are the channel drawn in the dark.

Every light has a rhythm

Lights are distinguished by their character: the pattern of flashes, the length of the interval and the colour. A light might flash in groups, occult by being on longer than off, or show a quick repeated flash.

The period is the time to complete the whole pattern, and it is published for every light on a chart. This is how a mariner tells one light from another when several are in view at once along a coast. From a quayside bench, timing a flash pattern against a watch is a straightforward and quietly satisfying exercise.

Lights that tell you where to steer

A sectored light shows different colours in different directions, typically white in the safe approach and red or green either side. A vessel that sees the colour change knows it has moved off the approach line without needing any other instrument. Leading lights work differently: two lights at different heights that line up vertically when you are on the correct track.

Both systems are visible from land, and both explain why lights on a hillside behind a harbour are placed where they are. They are also why some apparently random lights on a headland turn out to be the most important ones in the port.

Marks that say avoid this

Cardinal marks indicate the direction of safe water relative to a hazard, using distinctive flash patterns and a black and yellow scheme. An isolated danger mark sits on or over a specific hazard with navigable water all around it. Special marks in yellow indicate something other than navigation, such as an outfall, a cable or a restricted area.

Safe water marks, with their own pattern, indicate navigable water all around and often mark a channel entrance.

None of this is a substitute for a chart, and reading the system from shore is an interest rather than a qualification.

What it tells you about the town

The direction the leading lights point tells you exactly where the safe approach comes from and therefore where the swell does not. The height and range of the main light indicate how far offshore vessels need to pick the harbour up. A port with an elaborate lighting arrangement is one where the approach is difficult, which is a piece of local history.

When the wind turns, fog signals, where they still exist, mark places where visibility fails often enough to justify the installation. Reading all of that from a bench gives a better sense of a harbour's problems than any interpretation board.

Where the authoritative version lives

Charts, lists of lights and almanacs publish the character, height, range and sector of every navigational light. Harbour authorities publish their own entrance signals, which cover gate status, traffic direction and prohibitions.

Those local signals are specific to the port and cannot be interpreted using a general system at all. Notices to mariners record changes, and lights do change, so anything memorised has a shelf life. For a visitor the value is comprehension rather than navigation, and it turns a dark harbour mouth into something readable.

The takeaway

Sit on the quay at dusk with a watch, and the harbour entrance stops being decoration and becomes a set of instructions.

The best hours on any shore are the ones before the car parks fill.