What the COLREGs require when anchored: the day shape, the anchor light at night, fog signals, and where you may and may not anchor safely and legally.
Dropping the anchor and settling into a quiet bay is one of the great pleasures of boating, but an anchored vessel is not exempt from the rules. Under the COLREGs a vessel at anchor still has to make itself visible and audible to others, using a specific day shape, a night light, and a distinctive fog signal. Get these wrong and you risk both a collision and a mark against you on the exam, because anchoring signals are a common test topic. Get them right and you become a clearly marked, predictable feature of the seascape that others can safely avoid.
This guide covers the signals a vessel at anchor must display by day, by night and in fog, along with the good-seamanship considerations of where to anchor and how to do it safely.
It is easy to assume that once you stop, the rules stop mattering, but the opposite is true. A vessel at anchor is stationary in water where others are moving, sometimes at night or in fog, and other skippers need to know it is there and that it is not underway. The COLREGs therefore require anchored vessels to show clear signals so approaching vessels can identify them and give them room. An anchored vessel is not “underway” in the legal sense, and its signals tell others exactly that.
There is also a manoeuvring reason. A moving vessel can take avoiding action, but an anchored one cannot easily get out of the way. Making yourself unmistakably visible is part of taking your share of responsibility for avoiding a collision.
By day, a vessel at anchor displays a single black ball shape in the fore part of the vessel, where it can best be seen. This round black shape is the universally recognised signal that a vessel is anchored rather than underway. On a small boat it is often a folding or collapsible ball hoisted on the forestay or a halyard.
Displaying the ball is a legal requirement, not an optional courtesy, and it is regularly examined. If another skipper sees the anchor ball, they know instantly that you are stationary and holding position, which changes how they will pass you. Forgetting the ball is a classic real-world mistake and a favourite exam trap.
At night, a vessel at anchor shows an all-round white light where it can best be seen. This anchor light marks your position for approaching traffic. On a small vessel a single all-round white light at the masthead or hoisted high is typical.
Larger vessels, generally those of 50 metres or more, show two all-round white lights, one forward and one lower down aft, so their length and orientation are clearer. Very large vessels may also use working lights to illuminate their decks. For recreational purposes, the key point to remember is the single all-round white light, distinct from the coloured sidelights and masthead steaming lights that indicate a vessel underway. If you see only a white all-round light with no red or green sidelights, you are likely looking at an anchored vessel.
In restricted visibility, an anchored vessel cannot rely on being seen, so it announces its presence by sound. A vessel at anchor rings a bell rapidly for about five seconds at intervals of not more than one minute. This distinctive rapid ringing is the signal that a vessel is anchored somewhere in the fog ahead.
On larger vessels the signal is extended. A vessel of 100 metres or more rings the bell in the forward part and immediately follows it by sounding a gong rapidly for about five seconds in the after part, so the whole length of the vessel is announced. Any anchored vessel may also, in addition, sound one short, one prolonged and one short blast to warn an approaching vessel of its position. For a recreational skipper, the essential takeaway is the rapid bell every minute.
Beyond the required signals, good seamanship and local rules govern where you may anchor. A few principles keep you safe and legal.
Once anchored, keep a periodic watch to confirm you are not dragging, especially if wind or tide changes, and re-anchor if needed. An anchored vessel that drags becomes an unpredictable hazard.
Anchoring signals are precise and therefore easy to test: a black ball by day, an all-round white light by night, and a rapid bell in fog. Because the details are exact, a little targeted practice makes them stick. In the boatingexamine course you can drill anchoring and signal questions in exam format, so you can recall the correct shape, light and sound signal without hesitation on the day.
What day shape does an anchored vessel display? A single black ball, shown in the fore part of the vessel where it is most visible. This is the standard daytime signal that a vessel is at anchor rather than underway, and it is a common exam question.
What light does a boat at anchor show at night? An all-round white light where it can best be seen. Small craft typically show a single such light. Large vessels of 50 metres or more show two all-round white lights, one forward and one lower aft. The absence of coloured sidelights helps you identify an anchored vessel.
Can I anchor anywhere I like? No. Avoid anchoring in narrow channels, fairways, traffic separation schemes and harbour approaches, and respect charted anchoring prohibitions that protect cables, pipelines and sensitive seabed areas. Always choose safe holding ground with enough depth and swinging room, and check your local rules before dropping the hook.
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