Rule 30 — Anchored and Aground: Lights and Shapes

TL;DR — A vessel at anchor shows two all-round white lights (fore higher, stern lower); a vessel aground shows those same anchor lights plus two all-round red lights in a vertical line by night and three balls in a vertical line by day. Size thresholds and barge-specific provisions create the most-tested exceptions.

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What the Rule Says

Timing and applicability

All light rules, including Rule 30, must be complied with in all weathers from sunset to sunrise. 33 CFR §83.20 During daylight hours in restricted visibility, those lights shall also be exhibited if carried, and shapes are required by day. 33 CFR §83.20

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Vessels at anchor — standard display

A vessel at anchor shall exhibit, where it can best be seen: 33 CFR §83.30

1. In the fore part — an all-round white light, or one ball (daytime). 33 CFR §83.30 2. At or near the stern, at a lower level than the forward light — an all-round white light. 33 CFR §83.30

The key geometric requirement is that the forward light must be higher than the stern light. This two-light arrangement allows an observer to determine the vessel's heading at anchor.

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Small vessel option — under 50 meters

A vessel of less than 50 meters in length may substitute a single all-round white light placed where it can best be seen, in lieu of the two-light arrangement described above. 33 CFR §83.30 This is a permission, not a mandate — the vessel may still use the two-light arrangement.

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Deck illumination — 100 meters and over

A vessel at anchor may use available working or equivalent lights to illuminate her decks. A vessel of 100 meters or more in length shall illuminate her decks. 33 CFR §83.30 Note the distinction: permissive for all vessels, mandatory for vessels 100 m or greater.

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Vessels aground

A vessel aground shall exhibit the anchor lights appropriate to her length (the two-light arrangement under paragraph (a), or the single light under paragraph (b) if under 50 m), and in addition, if practicable, where they can best be seen: 33 CFR §83.30

• By night: Two all-round red lights in a vertical line. 33 CFR §83.30
• By day: Three balls in a vertical line. 33 CFR §83.30

The qualifier "if practicable" applies to the additional aground signals — the anchor lights themselves are not qualified.

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Exemptions by vessel length

| Situation | Vessel length | Exemption | |---|---|---| | At anchor, not in/near channel, fairway, anchorage, or area where vessels normally navigate | Less than 7 meters | No anchor lights or shapes required 33 CFR §83.30 | | At anchor in a special anchorage area designated by the Coast Guard | Less than 20 meters | No anchor lights or shapes required 33 CFR §83.30 | | Aground — additional red lights and balls | Less than 12 meters | Not required to exhibit the two red lights or three balls 33 CFR §83.30 |

Memorize these three length thresholds: 7 m, 12 m, and 20 m — each triggers a different exemption.

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Pilot vessels at anchor

A pilot vessel engaged on pilotage duty and at anchor must exhibit, in addition to her distinctive masthead lights (upper white, lower red), the anchor light, lights, or shape prescribed in Rule 30 for vessels at anchor. 33 CFR §83.29 A pilot vessel not on pilotage duty shows only the lights appropriate for a vessel of her length. 33 CFR §83.29

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Moored barges — Inland-specific provisions

Rule 30 contains detailed barge lighting requirements that are heavily tested for Inland waters. The following barges shall display the required lights at night and, if practicable, in restricted visibility: 33 CFR §83.30

• Every barge projecting into a buoyed or restricted channel. 33 CFR §83.30
• Every barge moored so that it reduces navigable width of any channel to less than 80 meters. 33 CFR §83.30
• Barges moored in groups more than two barges wide or to a maximum width of over 25 meters. 33 CFR §83.30
• Every barge not moored parallel to the bank or dock. 33 CFR §83.30

Barges meeting those criteria shall carry two unobstructed all-round white lights visible for at least 1 nautical mile, meeting Annex I technical requirements. 33 CFR §83.30

Barge exemptions — the following are exempt from Rule 30 lighting requirements: 33 CFR §83.30

• A barge or group of barges moored in a slip or slough used primarily for mooring purposes. 33 CFR §83.30
• A barge or group of barges moored behind a pierhead. 33 CFR §83.30
• A barge less than 20 meters in length when moored in a special anchorage area. 33 CFR §83.30
• Barges moored in well-illuminated areas specified in the Rule (certain reaches of the Chicago Sanitary Ship Canal, Calumet Sag Channel, Little Calumet River, Calumet River, and Cumberland River). 33 CFR §83.30

Barge or group at anchor or on mooring buoys — in lieu of the standard provisions, may carry all-round white lights (1 nm visibility, Annex I compliant) arranged so that: any barge projecting from a group formation is lighted on its outboard corners; a single barge navigated on both sides is lighted at corner extremities; a group navigated on both sides is lighted at the corner extremities of the group. 33 CFR §83.30

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Annex I placement note

All-round lights, including anchor lights, shall be located so as not to be obscured by masts, topmasts, or structures within angular sectors of more than 6 degrees. Anchor lights prescribed in Rule 30 are specifically excepted from the requirement to be placed at an impracticable height above the hull. 33 CFR §84.15 If a single all-round light cannot comply, two all-round lights suitably positioned or screened shall be used so as to appear as one light at a minimum distance of 1 nautical mile. 33 CFR §84.15

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Why It Matters on the Exam

Exam questions on Rule 30 typically test four areas:

1. The two-light vs. single-light threshold. The dividing line is 50 meters. Vessels under 50 m may use one all-round white light; vessels 50 m and over must use the two-light arrangement (fore higher, stern lower). 33 CFR §83.30

2. Aground signals. Candidates must know that a vessel aground shows anchor lights plus two all-round red lights (night) and three balls (day). The "if practicable" qualifier is frequently tested — the anchor lights themselves carry no such qualifier. 33 CFR §83.30

3. The three length-based exemptions. Questions will present a scenario (e.g., a 6-meter vessel anchored in a cove away from traffic) and ask what lights are required. Know 7 m, 12 m, and 20 m cold. 33 CFR §83.30

4. Deck illumination. The mandatory/permissive split at 100 meters is a classic distractor. "May" applies to all anchored vessels; "shall" applies only to those 100 m or more. 33 CFR §83.30

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Common Pitfalls

Pitfall 1 — Confusing the aground red lights with other red lights. Two all-round red lights in a vertical line mean aground. Do not confuse with the pilot vessel's lower red masthead light or with not-under-command lights (which are also two all-round red lights but are shown by an underway vessel). Context and the accompanying anchor lights distinguish the aground vessel.

Pitfall 2 — Forgetting that aground vessels still show anchor lights. The two red lights are additional to the anchor display, not a replacement. 33 CFR §83.30

Pitfall 3 — Misapplying the 7-meter exemption. The exemption for vessels under 7 meters applies only when the vessel is NOT in or near a narrow channel, fairway, anchorage, or area where other vessels normally navigate. A 5-meter vessel anchored in a fairway still must show anchor lights. 33 CFR §83.30

Pitfall 4 — Treating the single-light option as mandatory for small vessels. The rule says a vessel under 50 m "may exhibit" a single light. It is an option, not a requirement. 33 CFR §83.30

Pitfall 5 — Overlooking the "if practicable" qualifier on aground signals. The two red lights and three balls for a vessel aground are required only "if practicable." The anchor lights carry no such qualification. 33 CFR §83.30

Pitfall 6 — Ignoring the barge channel-width trigger. The 80-meter navigable-width threshold and the 25-meter group-width threshold are specific numbers the exam will test. 33 CFR §83.30

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Quick Check

Q1 — A 75-meter vessel is at anchor at night. What lights must she display?

She must display two all-round white lights: one in the fore part and one at or near the stern at a lower level than the forward light. Because she is 75 meters in length, she does not qualify for the single-light option (which is available only to vessels under 50 meters). She may also illuminate her decks, but is not required to do so (the mandatory deck illumination applies only to vessels 100 meters or more). 33 CFR §83.30

Q2 — A 110-meter vessel is at anchor. What is her obligation regarding deck lighting?

She shall use available working or equivalent lights to illuminate her decks. For vessels of 100 meters or more in length, deck illumination is mandatory, not optional. 33 CFR §83.30

Q3 — A vessel is aground at night. What lights does she display?

She displays the anchor lights appropriate to her length (two all-round white lights, fore higher than stern, for vessels 50 m or more; optionally a single all-round white light for vessels under 50 m) plus, if practicable, two all-round red lights in a vertical line. 33 CFR §83.30

Q4 — A 10-meter vessel is aground. Must she display the two all-round red lights?

No. A vessel of less than 12 meters in length when aground is not required to exhibit the two all-round red lights in a vertical line or the three balls in a vertical line. 33 CFR §83.30

Q5 — A 5-meter vessel is anchored in a quiet cove well away from any channel or area where vessels normally navigate. What anchor lights are required?

None are required. A vessel of less than 7 meters in length, when at anchor and not in or near a narrow channel, fairway, anchorage, or where other vessels normally navigate, is not required to exhibit anchor lights or shapes. 33 CFR §83.30

Q6 — A barge is moored at a right angle to the bank, projecting into a restricted channel. What lights must it display at night?

It must display two unobstructed all-round white lights of an intensity visible for at least 1 nautical mile, meeting Annex I technical requirements. This barge qualifies under both the "projecting into a buoyed or restricted channel" criterion and the "not moored parallel to the bank or dock" criterion. 33 CFR §83.30

Q7 — A pilot vessel is engaged on pilotage duty and is at anchor. What lights does she show?

She shows her distinctive masthead lights (upper all-round white, lower all-round red in a vertical line) plus the anchor light or lights prescribed by Rule 30 for a vessel of her length. 33 CFR §83.29 33 CFR §83.30

Q8 — A 15-meter vessel is anchored in a Coast Guard-designated special anchorage area. Must she display anchor lights?

No. A vessel of less than 20 meters in length, when at anchor in a special anchorage area designated by the Coast Guard, is not required to exhibit the anchor lights and shapes required by Rule 30. 33 CFR §83.30