Lights & shapes study overview

Identify vessel status, aspect and activity from lights and day shapes.

Practise observation and judgement using sailing scenarios. Interactive questions and your device-local progress load when JavaScript is available.

Study points

• A vessel’s port sidelight is red and its starboard sidelight is green. Assess all visible lights and motion.
• A vessel under sail while also propelled by machinery is power-driven for the collision regulations. The normal power-driven light requirements apply, including the appropriate masthead arrangement. Sails still being set does not preserve sailing status, and motorsailing is not itself restricted manoeuvrability. Small-vessel alternatives must be checked against their specific limits.
• Two all-round red lights in a vertical line identify a vessel not under command, subject to the prescribed additional lights/shapes.
• Three all-round red lights in a vertical line identify a vessel constrained by her draught. Do not confuse this with two red lights for not under command.
• An anchored vessel displays the prescribed anchor light(s) or shapes, with additional requirements depending on vessel length and circumstances.
• The period is the time for the complete recurring character, including flashes and eclipses. Confirm identity with position, bearing and range.
• Lights and shapes provide status and aspect clues, but do not by themselves prove identity, position or a safe passing distance.
• A power-driven vessel underway generally displays masthead light(s), sidelights and a sternlight, with details depending on vessel length and activity.

Educational revision only. Check current official rules, charts and publications before navigating.