BOAT-COMPARATOR Guide

Navigation Lights at Night: Understanding Port, Starboard and Stern

Red on the left, green on the right, white astern: the navigation light code, simple once explained, essential the moment a trip runs past sunset.

At night a boat is no longer recognised by its shape but by its lights: one red dot, one green dot, one white dot are enough to work out its position and heading before you can even make out the hull. This code, fixed by international convention, reads in seconds once you know it — and becomes essential the moment an outing runs past sunset.

The colour code, in three points

• Red light on the port side (the left side of the boat, facing forward).
• Green light on the starboard side (the right side).
• White light at the stern or masthead, visible from behind.

What these colours tell you

If you see another boat's red light, you're looking at its left side: it's crossing your course from left to right, and it generally has right of way. Seeing its green light means the opposite. Seeing both coloured lights at once means it's heading straight at you, bow to bow. Seeing only its white stern light means it's moving away, in the same direction as you. Our guide to right-of-way rules at sea covers what to do in each case.

Letting your eyes adjust to the dark

Spotting a distant light requires eyes already adapted to darkness. A landmark study by British physiologist W.A.H. Rushton, published in 1961 (see the study on Google Scholar), measured that the human eye keeps gaining sensitivity to low light for 20 to 30 minutes after exposure to a bright light — a phone screen lit up on deck is enough to reset the clock. The right habit: dim every screen, use a torch in red mode if you have one, and give your eyes a few minutes before scanning the horizon.

What a rental boat must carry

Regulation navigation lights are part of the mandatory safety equipment checked at departure along with the rest of the gear. A light that won't switch on should be flagged to the operator before casting off, not discovered in the middle of the night.

What the rental contract actually allows

Many rental boats, day boats especially, are required to be back at the dock before dark: night sailing isn't automatically included in the contract. Our guide to night sailing on a rental boat covers what operators actually allow, and under what conditions.

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