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Rule 30: Anchored Vessels and Vessels Aground (COLREGS)

Last reviewed October 21, 2026

The short answer

Rule 30 says a vessel at anchor shows an all-round white light or one ball forward and a lower all-round white light at the stern. Under 50 meters, one all-round white light will do. A vessel aground adds two all-round red lights in a vertical line, or three balls by day.

The rule text

A vessel of less than 50 meters in length may exhibit an all-round white light where it can best be seen instead of the lights prescribed in paragraph (a) of this Rule.

International Rules, U.S. Coast Guard Navigation Rules and Regulations Handbook (NAVCEN, 2024 corrected edition), Rule 30

A vessel aground shall exhibit the lights prescribed in paragraph (a) or (b) of this Rule and in addition, where they can best be seen: (i) two all-round red lights in a vertical line; (ii) three balls in a vertical line.

International Rules, U.S. Coast Guard Navigation Rules and Regulations Handbook (NAVCEN, 2024 corrected edition), Rule 30

A vessel of less than 12 meters in length, when aground, shall not be required to exhibit the lights or shapes prescribed in subparagraphs (d)(i) and (ii) of this Rule.

International Rules, U.S. Coast Guard Navigation Rules and Regulations Handbook (NAVCEN, 2024 corrected edition), Rule 30

What it means on the water

  • At anchor: all-round white (or one ball by day) forward, a lower all-round white at or near the stern (Rule 30(a)).
  • Under 50 meters: one all-round white light where it can best be seen (Rule 30(b)).
  • 100 meters or more must also illuminate her decks with working lights (Rule 30(c)).
  • Aground: anchor lights plus two all-round reds in a vertical line, and three balls by day (Rule 30(d)).
  • Exemptions: under 7 meters at anchor away from channels, fairways, anchorages and normal traffic (30(e)); under 12 meters aground (30(f)).

International vs Inland

Inland adds Rule 30(g): a vessel under 20 meters at anchor in a Coast Guard special anchorage area doesn't need anchor lights and shapes. Inland Rule 30 also adds lighting rules for certain moored barges. Inland 30(d) says the aground signals are shown "if practicable."

Common exam traps

  • Calling two all-round reds "not under command" when they're shown with anchor lights. That's aground.
  • Requiring two anchor lights on a vessel under 50 meters.
  • Forgetting the day shape for aground: three balls, not two.

Try 3 questions on Rule 30

  1. By day, a vessel aground shows:

    1. One ball
    2. Two balls
    3. Three balls
    4. Ball, diamond, ball
    Show answer

    C. Three balls Rule 30(d)(ii).

  2. A 35-meter vessel at anchor at night may show:

    1. One all-round white light
    2. Two all-round red lights
    3. A sternlight only
    4. Sidelights
    Show answer

    A. One all-round white light Rule 30(b).

  3. Which vessel must light her decks at anchor?

    1. Any vessel over 20 meters
    2. A vessel 100 meters or more
    3. Only a fishing vessel
    4. None
    Show answer

    B. A vessel 100 meters or more Rule 30(c).

Frequently asked questions

What day shape shows a vessel at anchor?

One ball in the fore part (Rule 30(a)(i)).

What lights does a vessel aground show?

Her anchor lights plus two all-round red lights in a vertical line (Rule 30(d)).

Do small boats need anchor lights?

Under 7 meters, not when anchored away from channels, fairways, anchorages, and where vessels normally navigate (Rule 30(e)). Inland 30(g) also exempts vessels under 20 meters in special anchorage areas.

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