Anchor light, anchor ball and moorings

Navigation Rules, lights & bridges · Power & sail

At anchor a boat shows an all-round white light at night and one black ball by day. On Inland waters a boat on a mooring buoy counts as anchored. Inland Rules exempt boats under 20 meters (65.6 ft) anchored in a Coast Guard special anchorage area (Inland Rule 30; 33 CFR 90.5, 110.1).

Commonly missed

Many owners never hoist an anchor ball. Outside the exemptions above, the rule applies by day to every vessel at anchor, whatever her size.
A masthead tricolour or steaming light is not an anchor light. At anchor, switch them off and show the all-round white light.

At night

A vessel at anchor shows an all-round white light forward and a second, lower all-round white light at or near the stern. A vessel under 50 meters may instead show one all-round white light where it can best be seen (Inland Rule 30(a)-(b)).
On a vessel under 50 meters that all-round light must be visible for at least 2 nautical miles (Inland Rule 22(b)-(c)).

By day: the anchor ball

By day a vessel at anchor shows one ball in the fore part where it can best be seen (Inland Rule 30(a)(i)).
Shapes are black. A full-size ball is at least 0.6 meter [about 2 ft] across, but a vessel under 20 meters may use a smaller ball in proportion to her size (33 CFR 84.06(a), (c)).

Moorings and special anchorage areas

On Inland waters a vessel made fast to one or more mooring buoys counts as a vessel at anchor, so the anchor light and anchor ball rules apply (33 CFR 90.5).
Inland only: a vessel under 20 meters (65.6 ft) at anchor in a special anchorage area designated by the Coast Guard need not show anchor lights or shapes (Inland Rule 30(g); 33 CFR 110.1(a)). The areas are listed in 33 CFR part 110, subpart A.
In those special anchorage areas, the same boats are also excused from the anchor bell signal in restricted visibility (Inland Rule 35(l); 33 CFR 110.1(a)).
The International Rules have no special-anchorage exemption.

Small-boat exemption and running aground

A vessel under 7 meters [23 ft] need not show anchor lights or the ball when anchored away from narrow channels, fairways, anchorages and places where other vessels normally navigate (Inland Rule 30(e)). Any boat 25 ft or longer is over 7 meters, so this never applies to her.
A vessel aground shows her anchor light(s) and, if practicable, two all-round red lights in a vertical line at night and three balls in a vertical line by day (Inland Rule 30(d)).
A vessel under 12 meters (39.4 ft) need not show the extra red lights or the three balls when aground (Inland Rule 30(f)).

The rules: Inland Rule 22 · Inland Rule 30 · Inland Rule 35 · 33 CFR 84.06 · 33 CFR 90.5 · 33 CFR 110.1

Sources (11)

ecfr.gov · ecfr.gov · ecfr.gov · ecfr.gov · ecfr.gov · ecfr.gov · ecfr.gov · navcen.uscg.gov · app.leg.wa.gov · boatus.org · ohiodnr.gov

A plain-language summary of federal rules for recreational boats, checked against the rules’ own text and a second source, and written in our own words. It isn’t legal advice. States add rules of their own, and rules change — the links above go to the current official text.