Special Operations: Towing, Fishing, and Restricted Vessels
Introduction to Special Status Vessels
The Navigation Rules recognize that certain vessels, due to their operations or conditions, have limited maneuverability and therefore require special visual signals to warn other traffic. These "special status" vessels display distinctive light patterns that immediately communicate their condition and claim priority in the vessel hierarchy established by Rule 18.
This lesson covers the critical light configurations for vessels engaged in towing, fishing operations, vessels not under command, vessels restricted in their ability to maneuver, and vessels constrained by draft. Understanding these configurations is essential because encountering these vessels requires specific actions and gives them right-of-way priority over normal power-driven and sailing vessels.
Vessels Towing and Pushing (Rule 24)
Rule 24 governs power-driven vessels engaged in towing or pushing operations. Towing is one of the most hazardous operations on the water, and the lights are designed to clearly communicate the towing configuration to prevent other vessels from attempting to cross between the tug and its tow.
The Distinctive Towing Signal: Vertical Masthead Lights
The key identifier of a towing vessel is two or three masthead lights in a vertical line instead of the single masthead light shown by normal power-driven vessels.
For a vessel towing astern (tow length 200 meters or less):
- Two white masthead lights in a vertical line forward
- Sidelights
- Sternlight
- Yellow towing light above the white sternlight
For a vessel towing astern (tow length exceeds 200 meters):
- Three white masthead lights in a vertical line forward
- Sidelights
- Sternlight
- Yellow towing light above the white sternlight
- Diamond day shape (both tug and tow must display)
Mnemonic: "Two masts, towing; three masts, long towing"
The yellow towing light is positioned above the sternlight with the same 135° arc, clearly visible from astern. This yellow light is the definitive indicator that a tow exists behind the vessel.
Pushing Ahead or Towing Alongside
For vessels pushing ahead or towing alongside (where tug and tow are rigidly connected):
International Rules: Two white masthead lights in vertical line (same as towing astern)
Inland Rules (US waters): Two yellow all-round lights in vertical line instead of white masthead lights, PLUS normal power vessel lights.
Mnemonic (Inland): "Yellow over Yellow, Pushing Fellow"
This Inland variation exists because pushed barges on rivers are extremely common, and the distinctive yellow lights prevent confusion with large vessels showing two white masthead lights (which could be a vessel over 50 meters).
The Towed Vessel's Lights
The vessel or object being towed must display:
- Sidelights (if vessel)
- Sternlight (if vessel)
- Diamond day shape (if tow exceeds 200m)
If the towed object is partially submerged or has low profile:
- All-round white lights at forward and aft ends, plus sidelights if width exceeds 25 meters
Critical Safety Point: Never attempt to cross between a tug and its tow. The towing hawser (cable) may be submerged and invisible, and vessels have been capsized by running into submerged towing cables at speed.
Vessels Engaged in Fishing (Rule 26)
Rule 26 distinguishes between vessels engaged in trawling and vessels fishing with other gear. This distinction exists because trawling (dragging nets through the water) restricts maneuverability more severely than line fishing.
Trawling
A vessel engaged in trawling shall exhibit:
- Green all-round light over white all-round light (vertical)
- Sidelights and sternlight (when making way)
Mnemonic: "Green over White, Trawling Tonight"
Fishing (Not Trawling)
A vessel engaged in fishing other than trawling shall exhibit:
- Red all-round light over white all-round light (vertical)
- Sidelights and sternlight (when making way)
Mnemonic: "Red over White, Fishing at Night"
Additional Signals for Fishing Vessels
When outlying gear extends more than 150 meters horizontally from the vessel, the fishing vessel shall exhibit in the direction of the gear:
- One white all-round light (or white cone apex upward day shape)
This warns other vessels: "Don't pass on this side-my nets/lines extend in this direction."
Vessels Under 20 Meters Fishing
Small fishing vessels under 20 meters may, instead of the lights above, exhibit:
- One all-round white light (and sidelights and sternlight when making way)
This simplification recognizes the limited electrical capacity of small commercial fishing boats.
Vessels Not Under Command (NUC) (Rule 27a)
A vessel Not Under Command is "a vessel which through some exceptional circumstance is unable to maneuver as required by the rules and is therefore unable to keep out of the way of another vessel."
Examples of NUC conditions:
- Propulsion failure (engine breakdown, prop loss, fuel starvation)
- Steering failure (rudder loss, steering system failure)
- Major flooding requiring all attention to pumps
- Medical emergency requiring full crew attention
- Fire on board consuming all crew resources
NUC Lights (Rule 27a)
A vessel not under command shall exhibit:
- Two red all-round lights in vertical line where they can best be seen
- Sidelights and sternlight (when making way)
- Two black balls in vertical line (day shape)
Mnemonic: "Red over Red, Captain is Dead" (meaning the vessel's command/control is "dead")
When NOT making way (dead in the water): Show only the two red lights, no sidelights or sternlight.
Priority in Vessel Hierarchy
NUC vessels have the highest priority in Rule 18. All other vessels must keep clear. A NUC vessel cannot maneuver to avoid you-you must avoid it regardless of your own vessel type or the crossing/meeting situation.
Vessels Restricted in Ability to Maneuver (RAM) (Rule 27b)
A vessel Restricted in Ability to Maneuver includes vessels engaged in:
- Laying, servicing, or picking up navigation marks, cables, or pipelines
- Dredging, surveying, or underwater operations
- Replenishment, transfer of persons, cargo, or fuel at sea
- Launching or recovering aircraft
- Minesweeping operations
- Towing operations that severely restrict the vessel's ability to deviate from course
RAM Lights (Rule 27b)
A vessel restricted in ability to maneuver shall exhibit:
- Red-White-Red all-round lights in vertical line (three lights total)
- Sidelights and sternlight (when making way)
- Ball-Diamond-Ball in vertical line (day shape)
Mnemonic: "Red, White, Red, Restricted Ability Ahead"
When NOT making way: Show only the red-white-red lights, no sidelights or sternlight.
Additional Signals for Specific Operations
Vessel engaged in dredging or underwater operations (Rule 27d):
In addition to the RAM lights (red-white-red), the vessel shall exhibit:
- On the obstructed side: Two red all-round lights in vertical line, OR two black balls in vertical line (day)
- On the safe passage side: Two green all-round lights in vertical line, OR two black diamonds in vertical line (day)
This creates a clear traffic-directing system:
- "Red/balls = don't pass this side (obstruction)"
- "Green/diamonds = safe to pass this side"
Vessel engaged in diving operations:
Must display the International Code Flag "A" (Alpha flag: white and blue, swallowtail) in addition to RAM lights. This rigid replica flag must be at least 1 meter in height. Many states also require the diver-down flag (red with white diagonal stripe), though this is a state requirement, not a federal Navigation Rules requirement.
Vessels Constrained by Draft (CBD) (Rule 28) - International Rules Only
This rule applies ONLY in International Waters, NOT in US Inland Waters.
A vessel Constrained by Draft is "a power-driven vessel which, because of her draft in relation to the available depth and width of navigable water, is severely restricted in her ability to deviate from the course she is following."
Example: A fully loaded bulk carrier or supertanker entering a harbor approach channel. The vessel is drawing 50 feet and the channel depth is 52 feet. The vessel has only 2 feet of underkeel clearance and cannot safely deviate from the channel centerline.
CBD Lights (Rule 28)
A vessel constrained by draft may display, in addition to normal power-driven vessel lights:
- Three red all-round lights in vertical line
- Cylindrical day shape (black)
Mnemonic: "Three Reds in a Row, No Room Below"
Important Limitations
- International waters only: This rule does NOT exist in Inland Rules and is specifically excluded from US waters.
- Optional, not mandatory: The vessel "may" display these lights-it's not required
- Hierarchy: In International waters, CBD vessels have priority over power and sailing vessels but must give way to NUC and RAM vessels
Practical Implication: Small recreational vessels operating in International waters (offshore, approaching from sea) should understand that large vessels displaying three red vertical lights are claiming CBD status and cannot deviate from their course. Give them maximum clearance.
Summary and Recognition
Understanding special operation lights requires memorizing the key patterns:
Towing:
- Two or three white vertical masthead lights + yellow towing light = towing astern
- Yellow over yellow (Inland) = pushing ahead
Fishing:
- Green over white = trawling
- Red over white = fishing (not trawling)
Hampered Vessels (cannot maneuver):
- Red over red = Not Under Command
- Red-white-red = Restricted in Ability to Maneuver
- Three reds vertical = Constrained by Draft (International only)
Dredging:
- Red-white-red (RAM) PLUS two reds (obstruction side) and two greens (safe side)
All of these vessels claim priority in Rule 18 and must be given wide berth. When you see any of these distinctive light patterns, immediately assess the situation, slow down, and plan your maneuver to keep well clear.
Key Takeaways
- Towing vessels display two (or three if tow >200m) vertical white masthead lights plus yellow towing light
- Inland pushing vessels display yellow over yellow instead of white masthead lights
- Never cross between tug and tow-towing cables are often submerged and invisible
- Trawling vessels show green over white; other fishing vessels show red over white
- Vessels Not Under Command (NUC) show two red vertical lights-they cannot maneuver
- Vessels Restricted in Ability to Maneuver (RAM) show red-white-red vertical lights
- Dredging vessels add two reds (obstruction) and two greens (safe passage) to RAM lights
- Vessels Constrained by Draft (three red vertical) exist only in International waters
- All special operation vessels have priority in Rule 18 hierarchy-give them wide berth