COLREGS Rule 30 — Navigation Lights
Vessel at Anchor — Navigation Lights (COLREGS Rule 30)
A vessel at anchor shows all-around white anchor light(s). Vessels under 50 meters show one all-around white light positioned where it can best be seen. Vessels 50 meters or more show two — a higher one forward and a lower one aft. Vessels over 100 meters should illuminate their decks. No sidelights, sternlight, or masthead lights are shown at anchor.
Condition: At anchor at night or in restricted visibility
Navigation lights required
| Light | Color | Arc | Position |
|---|---|---|---|
| All-around white light (vessels under 50 m) | White | 360° | Where it can best be seen |
| All-around white light — forward (vessels 50 m or more) | White | 360° | Forward, at a higher point |
| All-around white light — aft (vessels 50 m or more) | White | 360° | At or near the stern, at a lower level than the forward light |
All-around white light (vessels under 50 m): One all-around white light is sufficient for vessels under 50 m
All-around white light — forward (vessels 50 m or more): Required for vessels 50 m or more; the forward light is the higher of the two
All-around white light — aft (vessels 50 m or more): Required for vessels 50 m or more in addition to the forward light
Dayshapes
| Shape | Position | When displayed |
|---|---|---|
| One black ball | Forward, where it can best be seen | During daylight hours when at anchor |
Exceptions and size rules
- →Vessels over 100 meters must illuminate their decks when at anchor.
- →Vessels at anchor may also use working lights to illuminate their decks.
- →In a special anchorage designated by the appropriate authority, vessels under 20 m are not required to show anchor lights or shapes.
Inland Rules differences
- !US Inland Rules are essentially the same for anchor lights. In certain designated anchorage areas, vessels under 20 m are exempt from anchor lights.
Common exam mistakes
- ✗Giving a vessel under 50 m two anchor lights — under 50 m only one all-around white is required.
- ✗Showing sidelights or a sternlight at anchor — no sidelights, sternlight, or masthead lights are displayed at anchor.
- ✗Confusing the anchor ball (one ball) with the aground dayshape (three balls) or NUC (two balls).
- ✗Forgetting that the two-light configuration (fore/aft) requires the forward light to be HIGHER than the aft light.
USCG exam questions — Vessel at Anchor
These questions are drawn from the same pool used in real USCG licensing exams. Correct answers and explanations are shown.
1. A vessel at anchor shall show by night:
- A.An all-round white light where it can best be seen
- B.An all-round white light forward and an all-round white light aft, the after light being lower✓
- C.Sidelights and an all-round white light
- D.A flashing white light
Why: Rule 30(a) requires an anchored vessel to show an all-round white light in the fore part of the vessel and a second all-round white light at or near the stern, lower than the forward light. This two-light combination helps observers judge the vessel's length and orientation.
2. A vessel less than 50 meters in length at anchor may, instead of the two prescribed anchor lights, show:
- A.A flashing white light
- B.A red over white all-round light
- C.A single all-round white light where it can best be seen✓
- D.Sidelights only
Why: Rule 30(b) allows vessels less than 50 meters at anchor to show just one all-round white light where it can best be seen, instead of the two-light forward/aft arrangement required for larger vessels.
3. A vessel aground at night shall show the anchor lights PLUS:
- A.Two all-round red lights in a vertical line✓
- B.A red flashing light
- C.Three all-round red lights in a vertical line
- D.A ball-diamond-ball sequence
Why: Rule 30(d)(i) requires a vessel aground to show the appropriate anchor lights (one or two all-round white lights) PLUS two all-round red lights in a vertical line. These red lights warn other mariners that the vessel is not merely at anchor but is stranded and completely immovable.
4. By day, a vessel aground shall display:
- A.Three black balls in a vertical line✓
- B.Two black balls in a vertical line
- C.A cylinder shape
- D.A black ball and a cylinder
Why: Rule 30(d)(ii) requires a vessel aground to display three black balls in a vertical line by day. This contrasts with the anchor shape (one black ball) or NUC (two balls), making three balls the unambiguous 'stuck on the bottom' signal.
5. By day, a vessel at anchor shall display:
- A.One black ball in the fore part of the vessel✓
- B.Two black balls in a vertical line
- C.A black cone, apex downward
- D.A black cylinder
Why: Under COLREGS Rule 30(a)(i), a vessel at anchor shall exhibit in the fore part, where it can best be seen, an all-round white light or one ball — so by day the required shape is a single black ball forward. (Two/three balls and the cone or cylinder denote other conditions: three vertical balls = aground per Rule 30(d), a cone apex-down = a sailing vessel proceeding under sail and power per Rule 25(e), and a cylinder = a vessel constrained by her draft per Rule 28.)
6. A vessel of 50 meters or more in length at anchor shall exhibit which lights?
- A.A forward all-round white light and an aft all-round white light lower than the forward one✓
- B.A single all-round white light visible all around the horizon
- C.Two all-round white lights of equal height
- D.A forward all-round white light and an all-round red light aft
Why: Rule 30(a) requires a vessel of 50 meters or more at anchor to exhibit a white all-round light forward and a second all-round white light at or near the stern at a lower height than the forward light, creating a distinctive anchor light profile.
7. A vessel aground shall exhibit which lights in addition to the anchor lights prescribed by Rule 30?
- A.Two all-round red lights in a vertical line✓
- B.Two all-round red lights and sidelights
- C.Three all-round red lights in a vertical line
- D.One all-round red light
Why: Under COLREGS Rule 30(d)(i), a vessel aground exhibits the anchor lights required by Rule 30(a) or (b) plus two all-round red lights in a vertical line (and, by day, three balls in a vertical line per 30(d)(ii)). These are a status signal identifying the vessel as aground — not a distress signal (distress signals are separately listed in Annex IV) — and do not denote not-under-command or restricted ability to maneuver under Rule 27.
8. A vessel of less than 50 meters in length at anchor shall exhibit which light?
- A.A single all-round white light where it can best be seen✓
- B.Two all-round white lights — one forward, one aft
- C.A white masthead light only
- D.A flashing all-round white light
Why: Rule 30(b) requires a vessel under 50 meters at anchor to exhibit a single all-round white light in the forward part of the vessel or where it can best be seen, simpler than the two-light requirement for larger vessels under Rule 30(a).
Frequently asked questions
- What lights does a vessel show when at anchor?
- A vessel under 50 meters shows one all-around white light positioned where it can best be seen. A vessel 50 meters or more shows two all-around white lights — one forward at a higher position and one aft at a lower level. No sidelights, sternlight, or masthead lights are displayed. During the day, one black ball is shown forward.
- Does a vessel at anchor show its running lights?
- No. An anchored vessel shows only all-around white anchor light(s) — no sidelights, no sternlight, no masthead lights. The only lights displayed are the anchor white light(s) and any working or deck lights.
- What is the dayshape for a vessel at anchor?
- A vessel at anchor displays one black ball forward where it can best be seen. This is different from the aground dayshape (three balls) and the NUC dayshape (two balls). The single ball is the standard anchor signal during daylight hours.
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