Module 5 - COLREGs
Yachtmaster COLREGs scenario: defend the decision
What you will learn
Rebuild the traffic plan when propulsion state, several contacts and a rain squall change the applicable COLREG framework during the encounter.
A defensible Yachtmaster response does not force a memorised label onto a changing scene. It states the evidence, protects control, assigns each contact its current rule framework and sets the observation that will trigger reassessment.
At night your sailing yacht is also being propelled by machinery, so it is a power-driven vessel for the Rules. A power-driven vessel visually in sight on the starboard bow holds a near-steady bearing while range decreases. A second vessel appears on radar and AIS ahead of the beam but cannot be seen inside a rain squall. A third light is closing on your port quarter and may be overtaking.
For the visually acquired power-driven crossing vessel, confirm the geometry and risk. If the crossing situation under Rule 15 is established, your yacht has the other vessel on her starboard side and must keep out of the way under Rule 16, taking early and substantial action and, if circumstances admit, avoiding crossing ahead. Do not let the presence of sails obscure the machinery-propelled classification.
The radar-only contact is different. Because it is not visually in sight in or near restricted visibility, do not assign it an in-sight stand-on or give-way role from AIS. Apply safe speed, proper lookout, systematic radar observation and Rule 19. If avoiding action is needed, choose it in ample time while respecting the Rule 19 course-alteration cautions and the geometry of every other contact.
Check whether the quartering contact is genuinely overtaking from visual evidence and whether its duty continues until finally past and clear. The manoeuvre for one contact must not create close quarters with another. If the rain squall removes visual contact with the crossing vessel, announce the change and reassess it under Rule 19; do not blindly continue an old Rule 15 label or manoeuvre.
Worked example
Give the first command brief for the three-contact scene before the squall reaches the visually acquired crossing vessel.
- 1State vessel status and evidence: power-driven, crossing contact visually in sight with collision risk, radar-only contact not in sight, quartering contact still being classified.
- 2Keep the crossing vessel out of the way with an early, substantial Rule 16 action that avoids crossing ahead if circumstances admit.
- 3Check the proposed action against the radar plot and the possible overtaker so it does not create a new close-quarters situation.
- 4Assign one person to the visual contacts and one to systematic radar observations; state the ordered action and the bearing, range or CPA trend expected next.
- 5Set the change trigger: loss of visual contact, an unexpected target response, inadequate clearance or a new risk causes immediate reappraisal rather than a delayed explanation.
Sense check: The first action is defensible only if it controls the known give-way duty and preserves safe options against the two uncertain contacts.
| Contact | Current framework | Immediate watch task |
|---|---|---|
| Starboard-bow power vessel, visually in sight | Rules 11–18; Rule 15/16 if the crossing geometry and risk are established | Take early keep-clear action and verify the bearing and range response |
| Ahead-of-beam radar-only contact in rain | Rules 4–10 and Rule 19; no in-sight stand-on/give-way role | Plot systematically and act in ample time if risk or close quarters develops |
| Port-quarter light | Rule 13 only if the in-sight overtaking definition is met | Confirm aspect and monitor until finally past and clear |
| Any contact lost from sight in the squall | Reassess under Rule 19 while in or near restricted visibility | Announce, replot, rebrief and verify the new plan |
Brief the visibility transition
The rain squall reaches the crossing vessel and it disappears from visual sight while remaining on radar.
1. Announce
State that visual contact has been lost and that the contact is now being assessed under the restricted-visibility framework.
2. Control
Reassess safe speed, engine readiness, lookout, radar set-up and the effect of the action already under way.
3. Replot
Use systematic radar observation to determine whether risk or close quarters remains and assess all contacts together.
4. Rebrief
State the next action, the Rule 19 cautions, the expected trend and the trigger to reduce speed, take all way off or act differently.
Sense check: Losing sight is an operational state change, not a reason to keep using an in-sight label because it was correct a minute earlier.
Common mistake or limitation
- A yacht using machinery is power-driven for the Rules even when sails remain set.
- An AIS vector does not make a radar-only target visually in sight or allocate Rule 15 and Rule 17 roles.
- The Rule 19 cautions are not automatic turn commands; the whole plot, sea room and other contacts still govern the action.
- This written scenario can rehearse rule selection and command language, but it cannot demonstrate lookout, radar use, practical judgement or Yachtmaster examination competence aboard.
Recap
- State own-vessel propulsion status before applying encounter rules.
- Give every contact its own evidence record and current visibility framework.
- Control the known duty without creating a new conflict with uncertain contacts.
- Treat loss of visual contact as a trigger to reassess, replot and rebrief under Rule 19.
Optional quick check
Section 14 of 14
The rain squall removes visual contact with the crossing vessel, although it remains on radar. What should the skipper do next?
Sources and factual review
Reviewed 2 September 2026 - Compass Revision editorial review.
Practice COLREGs under decision pressure
The full module adds steering rules, lights, shapes, restricted visibility and mixed encounter questions.