Stopped Vessels: Anchored, Aground, and Dredging

Introduction

Vessels that are stationary-whether anchored by choice, aground by accident, or engaged in dredging operations-present unique hazards to navigation. A vessel moving through the water can take action to avoid collision, but a stationary vessel cannot. Therefore, these vessels must display distinctive signals to clearly communicate their stopped condition and warn approaching traffic.

Rule 30 governs vessels at anchor and aground, while Rule 27(d) provides additional requirements for dredging vessels. Understanding these signals is critical for safe navigation, particularly when transiting harbors, anchorages, and channels where stopped vessels are common.

Vessels at Anchor (Rule 30)

A vessel at anchor must display specific lights and shapes based on its size to warn approaching vessels of its stationary position.

Vessels 50 Meters (164 ft) or More at Anchor

Large vessels at anchor shall exhibit:

At Night:

• One all-round white light in the forward part of the vessel where it can best be seen
• One all-round white light in the aft part of the vessel, lower than the forward light

By Day:

• One black ball in the forward part of the vessel where it can best be seen

The two anchor lights create a range system. From any angle of approach, a mariner can see at least one white light and, when viewing from ahead or astern, can see both lights with the forward light higher than the aft light. This vertical offset helps identify the vessel's orientation.

Additional Illumination: Vessels 100 meters or more in length shall also illuminate their decks with working lights to make the vessel's size and position clearly visible. This prevents vessels from attempting to pass close aboard, mistaking the anchored vessel for a smaller craft.

Vessels Under 50 Meters at Anchor

Smaller vessels at anchor shall exhibit:

At Night:

• One all-round white light where it can best be seen (typically on mast or arch)

By Day:

• One black ball where it can best be seen (typically on forestay or bow pulpit)

Simplification: Vessels under 50 meters are not required to show two anchor lights-one all-round white light is sufficient. However, they may display two lights if desired for increased visibility.

Special Anchorage Areas (33 CFR 110)

In designated Special Anchorage Areas (marked on charts and defined in 33 CFR 110), vessels under 20 meters in length are not required to display anchor lights or shapes. These areas are specifically designated for small craft anchorages in protected waters where traffic is minimal.

Important: Even in special anchorage areas, displaying an anchor light is always the safer choice and is considered good seamanship.

Vessels Under 7 Meters Not in a Channel

Vessels under 7 meters (23 feet) at anchor not in or near a narrow channel, fairway, or where other vessels normally navigate:

• Are not required to display anchor light or ball
• However: Must display an anchor light if in any area where other vessels navigate

Practical Application: A small sailboat anchored in a protected cove away from normal traffic may not need an anchor light. The same sailboat anchored in a harbor entrance, channel approach, or popular cruising route must display an anchor light.

Vessels Aground (Rule 30d)

A vessel aground is both anchored (fixed in place) and not under command (unable to maneuver). Therefore, its signals combine elements of both conditions.

Aground Signals

A vessel aground shall exhibit the lights and shapes of a vessel at anchor (Rule 30a, b, c) PLUS:

At Night:

• Two red all-round lights in vertical line where they can best be seen (the NUC signal)

By Day:

• Three black balls in vertical line where they can best be seen

The combination creates an unmistakable signal:

• Anchor light(s) = "I am stationary"
• Two red vertical lights = "I am not under command/cannot maneuver"
• Combined meaning = "I am stuck here and cannot move"

Why This Matters

A vessel aground typically extends beyond its normal draft, often sitting on a shoal, reef, or sandbar that may present a hazard to other vessels. The distinctive three-ball day shape and two-red-over-anchor-light night signal warns:

1. This vessel cannot move out of your way
2. The water here is shallow (the vessel is touching bottom)
3. Navigate carefully-you may also run aground here

Legal Obligation: All vessels seeing an aground vessel must keep well clear and navigate cautiously, as the grounding indicates shallow water or underwater obstructions.

Dredging and Underwater Operations (Rule 27d)

Dredging vessels and vessels engaged in underwater operations present a complex hazard: the vessel itself is restricted in maneuverability, AND it has underwater equipment and obstructions that extend outward, creating areas where passage is dangerous or impossible.

Dredging Vessel Lights

A vessel engaged in dredging or underwater operations, when restricted in ability to maneuver, shall exhibit:

The RAM signal (red-white-red vertical lights) described in Lesson 4, PLUS:

On the side where obstruction exists:

• Two red all-round lights in vertical line, OR
• Two black balls in vertical line (day)

On the side where passage is safe:

• Two green all-round lights in vertical line, OR
• Two black diamonds in vertical line (day)

Traffic Direction System

This creates a clear, unambiguous traffic-direction system:

Red/balls = DANGER - Obstruction exists - DO NOT PASS Green/diamonds = SAFE - Clear passage - Pass this side

The obstruction typically consists of:

• Submerged dredge pipeline extending to shore or disposal area
• Anchor cables and positioning equipment
• Underwater excavation creating shallow water
• Buoys, floats, and marker systems

Viewing a Dredge from Different Angles

Approaching from ahead or astern: You will see the red-white-red RAM lights (central vertical stack) plus either red or green lights on the sides depending on which side you're approaching.

Approaching from the safe passage side: You'll see green over green (safe passage indicator) plus the red-white-red RAM lights.

Approaching from the obstruction side: You'll see red over red (obstruction warning) plus the red-white-red RAM lights.

Important: The red obstruction lights are IN ADDITION to the RAM lights-you may see up to 5 red lights (2 red obstruction + 3 red-white-red RAM) when approaching the obstruction side.

Small Dredges and Vessels Under 12 Meters

Vessels engaged in diving operations or underwater work that are less than 12 meters in length are not required to display the ball-diamond-ball RAM day shape, but must display:

• The International Code Flag "A" (Alpha flag - rigid replica, 1 meter minimum height)
• The two-reds/two-greens obstruction/safe-passage indicators (if applicable)

Many states also require display of the "diver down" flag (red with white diagonal stripe), though this is state law, not federal Navigation Rules.

Practical Application and Safety

Anchored Vessels

When approaching an anchored vessel (single or double white lights with no red/green sidelights visible):

1. Identify: Lack of sidelights indicates vessel is not making way
2. Assess: Note the vessel's position relative to channels and your intended track
3. Plan: Alter course early to pass with ample clearance
4. Monitor: Watch for dragging (anchor not holding)-vessel may be drifting

Dragging Anchor Detection: If you see an anchor light that appears to be moving slowly, the vessel may be dragging its anchor. This is a navigation hazard, particularly in strong currents or high winds. Alert the vessel via VHF if possible.

Aground Vessels

When you see three black balls (day) or two red lights over anchor light (night):

1. Stop or slow immediately: The vessel is aground-there is shallow water or obstruction
2. Assess water depth: Check charts, depth sounder, and visual indicators
3. Alter course: Detour around the aground vessel with maximum clearance
4. Report: Notify harbor authorities or Coast Guard if the grounded vessel appears to present a hazard to navigation

Do NOT approach to offer assistance unless:

• You have local knowledge of water depths
• The grounded vessel is displaying distress signals (separate from aground signals)
• You have contacted them via VHF and they request assistance

Dredging Operations

When you see the ball-diamond-ball or red-white-red lights:

1. Identify the safe passage side: Look for green lights or diamond shapes
2. Do NOT attempt to pass on the obstruction side: Red lights or balls indicate danger
3. Pass with wide clearance: Even on the safe side, underwater equipment may extend farther than expected
4. Reduce speed: Create minimal wake to avoid disturbing dredging operations
5. Monitor VHF: Dredging operations often monitor and announce on VHF 13 or 16

Common Violations and Penalties

Failure to display anchor light: One of the most common lighting violations. Vessels anchored in harbors, channels, or near fairways without proper anchor lights create serious collision hazards. Penalties up to $18,610 per incident, plus liability for any resulting collision.

Improper anchor light placement: Anchor light must be visible from all directions (360°). Mounting inside the cabin or below lifelines where it's partially obscured violates Rule 30.

Failure to display black ball: Day shapes are just as mandatory as night lights. Anchored vessels must display the black ball between sunrise and sunset.

Summary

Vessels at anchor display one or two all-round white lights (depending on size) and a black ball by day. Vessels aground add two red vertical lights (night) or two additional balls for a total of three balls (day) to warn of their inability to maneuver and the shallow water.

Dredging vessels display the RAM signal (red-white-red) plus traffic direction indicators: two reds or two balls on the obstruction side, and two greens or two diamonds on the safe passage side.

All stopped vessels must be given wide berth. Their lights and shapes communicate critical information about stationary hazards and areas of restricted navigation.

Key Takeaways

• Vessels ≥50m at anchor show two white anchor lights (forward higher than aft) and black ball by day
• Vessels <50m at anchor show one white anchor light and black ball by day
• Vessels <7m not in channels may not need anchor light, but it's always safer to display one
• Vessels aground show anchor lights PLUS two red vertical (night) or three black balls (day)
• Aground signals warn of both stationary vessel and shallow water
• Dredging vessels use traffic direction system: red/balls = obstruction, green/diamonds = safe passage
• Always pass dredging operations on the green/diamond (safe) side with wide clearance
• Failure to display proper anchor lights is a common violation with serious safety and legal consequences