COLREGs
COLREGs: a method for reasoning through any situation
By Navisailor Learning Centre · Published 7 October 2026 · Updated 7 October 2026
The International Regulations for Preventing Collisions at Sea, usually called the COLREGs, are one of the most heavily tested subjects in any deck officer’s oral examination. They are also one of the easiest to answer badly, because candidates often recite rules without showing how they would apply them to a particular ship in particular conditions.
This guide gives you a structure for the regulations and a repeatable method for explaining a situation. It is a study aid, not a replacement for the text of the Convention. In Australia the regulations are given effect through Marine Order 30, and you should work from the current official text.
How the regulations are organised
The Convention is divided into parts. Part A covers application, responsibility and definitions. Part B contains the steering and sailing rules and is subdivided: Section I applies to conduct of vessels in any condition of visibility, Section II to conduct of vessels in sight of one another and Section III to conduct in restricted visibility. Part C covers lights and shapes, Part D covers sound and light signals and Part E covers exemptions. The annexes contain technical details and distress signals.
Knowing this structure helps you answer because you can say where a rule sits and why. Section II, for example, only applies when vessels are in sight of one another, whereas Section I always applies.
The rules that come first
Before any give-way or stand-on rule, a handful of rules in Section I set the foundation for every situation. Strong answers mention them without being asked.
Rule 5: lookout
Every vessel must at all times keep a proper lookout by sight and hearing and by all available means appropriate in the prevailing circumstances and conditions, so as to make a full appraisal of the situation and of the risk of collision.
Rule 6: safe speed
Every vessel must proceed at a safe speed so that she can take proper and effective action to avoid collision and be stopped within a distance appropriate to the prevailing circumstances. The rule lists the factors to consider, including visibility, traffic density, manoeuvrability, background light, the state of wind, sea and current, navigational hazards and draught in relation to the available depth of water.
Rule 7: risk of collision
Use all available means to determine whether risk of collision exists, and if there is any doubt, assume that it does. If the compass bearing of an approaching vessel does not appreciably change, risk of collision should be deemed to exist. Radar must be used properly, including long-range scanning and systematic observation, and assumptions on the basis of scanty information are to be avoided.
Rule 8: action to avoid collision
Any action should be positive, made in ample time and with due regard to the observance of good seamanship. Alterations of course or speed should be large enough to be readily apparent to another vessel observing visually or by radar, and a succession of small alterations should be avoided. The action should result in passing at a safe distance, and its effectiveness should be checked carefully until the other vessel is finally past and clear.
Vessels in sight of one another
Section II sets out who gives way to whom. Learn it as a short set of questions.
- Overtaking (Rule 13): any vessel overtaking another must keep out of the way. A vessel is overtaking when she comes up with another from a direction more than 22.5 degrees abaft the beam. If in doubt, assume you are overtaking.
- Head-on (Rule 14): when two power-driven vessels meet on reciprocal or nearly reciprocal courses so as to involve risk of collision, each alters course to starboard so that each passes on the port side of the other.
- Crossing (Rule 15): when two power-driven vessels cross so as to involve risk of collision, the vessel which has the other on her own starboard side keeps out of the way and, if the circumstances allow, avoids crossing ahead of the other vessel.
- Give-way vessel (Rule 16): take early and substantial action to keep well clear.
- Stand-on vessel (Rule 17): keep course and speed. The vessel may take action as soon as it becomes apparent that the give-way vessel is not taking appropriate action, and must take action to avoid collision by her manoeuvre alone when collision cannot be avoided by the give-way vessel’s action alone.
- Responsibilities between vessels (Rule 18): in general, a power-driven vessel gives way to a vessel not under command, a vessel restricted in her ability to manoeuvre, a vessel engaged in fishing and a sailing vessel, and the rule sets out the order for other types. Any vessel other than one not under command or restricted in her ability to manoeuvre must avoid impeding a vessel constrained by her draught.
Restricted visibility
Rule 19 applies to vessels not in sight of one another when navigating in or near an area of restricted visibility. Here there are no give-way and stand-on roles. Every vessel must proceed at a safe speed adapted to the circumstances and have her engines ready for immediate manoeuvre.
A vessel that detects another by radar alone must determine whether a close-quarters situation is developing or risk of collision exists, and if so take avoiding action in ample time. The rule also cautions against certain alterations: an alteration to port for a vessel forward of the beam, other than a vessel being overtaken, and an alteration towards a vessel abeam or abaft the beam. A vessel hearing the fog signal of another apparently forward of her beam, or unable to avoid a close-quarters situation with a vessel forward of her beam, must reduce speed to the minimum at which she can be kept on her course and, if necessary, take off all way.
A five-step method for any scenario
Whatever situation an examiner describes, work through the same steps, and say them aloud.
- Identify: what vessels are involved, what are they doing and what is the visibility? Say what you can see and by what means.
- Assess: is there risk of collision? Describe how you would tell, for example by watching the compass bearing and range over time.
- Rule: state which rule applies and which role you hold, such as give-way or stand-on.
- Act: say what you would do, when you would do it and how large the alteration would be. Remember Rule 8: early, substantial and readily apparent.
- Check: say how you would confirm that your action worked and what you would do if it did not, including calling the Master and using sound signals.
Practising effectively
Draw each situation on paper with the two vessels, their courses and the relevant arcs, then talk it through using the five steps. Vary the conditions: change visibility, vessel types, the available sea room and whether another vessel is present. Practise explaining how the rules interact with traffic separation schemes and narrow channels, and prepare to discuss the responsibilities of a stand-on vessel in more detail than most candidates expect. Use the current official text and Marine Order 30 for the exact wording.
Official sources
This guide was written from the following sources. Requirements change, so confirm the current position with the source before relying on it.
Related certificate guides
Keep reading
- COLREGs lights: a method for recognising vessels at night
- OOW and Watchkeeper Deck oral exam: the themes behind the questions
- Passage planning in four stages: appraisal, planning, execution and monitoring
- Maritime glossary for plain-language definitions of the terms used here.
- More in COLREGs, or browse the knowledge centre.
Independence note
Independent AMSA exam preparation platform by Navisailor Learning Centre. Not affiliated with or endorsed by the Australian Maritime Safety Authority. This guide is general study material. It is not legal advice, it is not official AMSA exam content, and it does not replace AMSA’s checklists, syllabi or the current legislation.