Yachtmaster COLREGs scenario: defend the decision

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.