Rule 30(a) — Anchored < 50 m
NIGHT. A stationary vessel is seen. She shows a SINGLE all-round WHITE light where it can best be seen. No sidelights, no sternlight, no red lights.
Scenario briefing
NIGHT. A stationary vessel is seen. She shows a SINGLE all-round WHITE light where it can best be seen. No sidelights, no sternlight, no red lights. Length is less than 50 m. What is her status?
Applicable COLREG rule(s)
📸 Night recognition — 8 aspects
The same vessel rendered every 45° of aspect — bow, starboard bow, beam, quarter, stern, port quarter, beam, bow. Use this strip to learn how the lights present from each approach angle. Click any image to view full size.
Key teaching points
- Rule 30(a)(i)/(b): a vessel under 50 m at anchor shows ONE all-round white light where best seen.
- No sidelights, no sternlight — the absence is part of the identification.
- Day equivalent: one black ball in the fore part.
- Compare to Rule 23(d)(ii) — a vessel under 7 m at less than 7 kt may also show a single all-round white; sidelights are then "if practicable".
Common mistakes to avoid
- Reading a single all-round white as a small PDV under 12 m — context (anchored area, ball-shape by day, position) breaks the ambiguity.
- Treating the anchor light as enough by day — Rule 30(a)(ii) requires the black ball.
Why it matters
Exam relevance
Small-vessel anchor lights and the Rule 23(d)(ii) confusion are a routine probe in Yachtmaster Coastal/Offshore orals.
Related scenarios
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