Module 1 - Nautical Terms
Port and Starboard
What you will learn
Use port and starboard as fixed vessel sides and keep vessel navigation lights separate from regional lateral buoyage colours.
Port and starboard remove the ambiguity of left and right because they belong to the vessel, not to the person looking at it.
Face the bow: port is the vessel's left side and starboard is its right side. The names do not swap when you turn to face aft, cross the cockpit or look at the vessel from ashore.
Under the COLREGs, a vessel's port sidelight is red and its starboard sidelight is green. Those light colours identify the vessel's sides; they are not instructions about which side of another vessel to pass.
Lateral marks belong to the IALA buoyage system and depend on the applicable region and direction of buoyage. In Region A, port-hand marks are red and starboard-hand marks green in the direction of buoyage; Region B reverses those lateral-mark colours. Vessel sidelights do not reverse between those regions.
Brief a side without relying on viewpoint
At night, the skipper asks for a lookout report. 'A green light on our port bow' distinguishes the observed light colour from its position relative to your own vessel.
1. Name your own side
Use port or starboard for the side of your vessel, regardless of where the observer is facing.
2. Describe the observation
Keep the colour or identity of another light or mark separate from its relative position.
3. Check the system
For a lateral mark, confirm the IALA region and direction of buoyage instead of applying the vessel-light mnemonic.
Sense check: A colour can describe a vessel light or a buoy; it does not replace the need to identify which system and viewpoint apply.
Common mistake or limitation
- Port does not become starboard when you face aft. Your personal left and right change; the vessel's sides do not.
- Red-to-port and green-to-starboard vessel sidelights are not a universal lateral-buoy rule. Region B reverses lateral-mark colours, not vessel sidelights.
Recap
- Port and starboard are fixed sides of the vessel.
- A vessel's port sidelight is red and starboard sidelight is green under the COLREGs.
- Lateral-mark colours require the applicable IALA region and direction of buoyage.
Optional quick check
Section 2 of 9
You turn to face the stern. What happens to the vessel's port side?
Sources and factual review
Reviewed 2 September 2026 - Compass Revision editorial review.
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