A dredger displaying a day shape of ball-diamond-ball on its mast indicating she is restricted in her ability to maneuver due to the nature of her work.

Identifying Ship’s Lights, Shapes, and Sound Signals

While many ships today upgrade their navigational tools to the latest technology, knowing the lights, shapes, and sound signals is as important as ever.

You will find detailed explanations in Parts C and D of COLREGS or the International Regulations for Preventing Collisions at Sea.

But since that regulation is rich in words and not images, I’ll be showing you how to determine which signals to use on a particular ship under specific conditions.

Power-Driven Vessels Underway

Under Rule 23 or COLREGS, a power-driven vessel (PDV) underway is a ship propelled by machinery that is not moored to any fixed installation, aground, or anchored.

Light Signals

Power-driven vessels are easily identified at night. Since they are the most common types of merchant ships, you will encounter them at sea.

PDVs exhibit a forward mast headlight, an aft mast headlight, sidelights, and a sternlight.

If the ship is less than 50 meters in length, he can exhibit one masthead light, with the second one being optional.

Power driven vessels underway showing different light signals- one with a single masthead light and another has two.

Day Shapes

You can not see any day shape on normal power-driven vessels since the vessel’s figure and movements indicate that it is a PDV. 

A power driven cargo vessel navigating in broad daylight. She is not displaying any day shape.
A power driven vessel cargo ship has no day shape.

Sound Signals

During restricted visibility, a power-driven vessel shall sound one prolonged blast at intervals of not more than two minutes.

Sailing Vessels

Under Rule 25 or COLREGS, Sailing Vessels or sailboats are ships powered by the wind using their sails to travel and move on the water.

Because their maneuverability depends entirely on the wind’s direction, they can not easily keep clear and have some leeway when met with specific types of vessels.

Light Signals

Sailing vessels have similar light configurations to power-driven vessels. The difference is that sailing vessels don’t show masthead lights.

In addition to sidelights and a sternlight, sailing vessels’ most distinct light display is a combination of all-round RED OVER GREEN lights near the top of the mast.

Three sailing vessels displaying various combinations of navigational lights.

Day Shape

During daytime, sailing vessels are easy to spot.

In addition to its obvious sail and if the ship is under power, sailing vessels must display an inverted cone shape.

Meaning, the cone must be displayed with its apex pointing downward.

A sailing vessel showing displaying her day shape of a black cone pointing downward.

Sound Signals

During reduced visibility, sailing boats must sound one prolonged blast followed by two short blasts at intervals of not more than two minutes.

One prolonged blast plus two short blast is actually a Morse signal “Delta (D),” meaning “Keep clear of me; I am maneuvering with difficulty.”

A sailing vessel navigating on a thick fog.

Fishing Vessels

There are two types of fishing vessels defined under Rule 26 of the COLREGS or International Regulations for Preventing Collisions at Sea.

While both boats are fishing, they use different apparatuses to catch fish. Hence, they display different light signals to identify one from another.

However, they use the same day shape and sound signal.

Fishing Vessels Engaged in Trawling

A fishing vessel engaged in trawling refers to a fishing boat dragging its dredge net or other apparatus used as a fishing appliance through the water.

Therefore, a fishing vessel engaged in trawling is a boat actively using a trawl net to catch fish.

Light Signals

Whatever type of fishing vessel you see in trawling, expect an all-round GREEN LIGHT OVER WHITE LIGHT in a vertical line.

Light signals for trawlers vary depending on their length, the state of their fishing apparatus, and whether they are engaged in pair trawling.

Just remember that fishing trawlers must display two all-round lights one above the other, the upper being green and the lower white.

Light displays for fishing vessels engaged in trawling. All of them shows red over green light on the mast.

Day Shapes

During the day, all types of fishing vessels shall display a shape consisting of two cones with their apexes together in a vertical line, one above the other.

As you may have already noticed, light signals and day shapes indicate the navigational status of vessels.

While we know this from the Automatic Identification System (AIS), note that not all vessels may have them.

An actual fishing vessel showing a day shape of two cones with their apexes together.

Sound Signals

The sound signal for all fishing vessels is one prolonged blast followed by two short blasts at intervals of not more than two minutes.

Fishing Vessels other than trawling

Fishing boats other than trawling use other fishing apparatus to catch fish, such as purse seines, long lines, gillnets, jiggers, and trollers.

Light Signals

Fishing vessels other than trawling shall exhibit two all-round lights in a vertical line, the upper being red and the lower white.

This is in addition to their sidelights, sternlight, and corresponding masthead lights.

A fishing vessel other than trawling showing navigational lights and a red over white light displayed on the mast.

Day Shapes

Fishing boats other than trawlers hall display a shape consisting of two cones with their apexes together in a vertical line, one above the other.

Sound Signals

The sound signal for all types of fishing vessels is one prolonged blast followed by two short blasts at intervals of not more than two minutes.

Vessels Not Under Command (NUC)

A vessel not under command (NUC) means a ship which through some exceptional circumstance, is unable to maneuver as required by COLREGs and is therefore can not keep out of the way of another vessel.

A NUC ship could be experiencing an engine breakdown, rudder failure, power blackout, flooding, or other emergencies that inhibit the ship from maneuvering.

Light Signals

Under Rule 27 of COLREGs, a vessel not under command shall display two all-round red lights one above the other where it can best be seen. To easily identify, red over red, Captain’s Dead.

If the ship is underway, she must exhibit sidelights and sternlights.

Two ships not under command (NUC) showing two red lights on a vertical line. One has navigational lights while the other has no navigational lights.

Day Shapes

The day shape for a vessel not under command is two black balls in a vertical line where they can best be seen.

A blue cargo ship showing two black balls on its mast indicating she is not under command (NUC).

Sound Signals

Just like other vessels maneuvering with difficulty, the sound signal for a vessel not under command is one prolonged blast followed by two short blasts at intervals of not more than two minutes.

Vessels Restricted in Their Ability to Maneuver (RAM)

A vessel is restricted in her ability to maneuver means a ship, due to the nature of her work, is restricted in her ability to maneuver as required by COLREGs and is, therefore, unable to keep out of the way of another vessel.

Light Signals

The light signals for a ship restricted in her ability to maneuver or RAM are three all-round lights in a vertical line, the highest and lowest of these lights are red, and the middle light is white.

A RAM vessel could be towing, dredging, engaged in diving operations, or conducting replenishments at sea.

If you see red-white-red lights in a vertical line, expect to keep a wide berth since this vessel can not keep out of her way.

Different vessels restricted in their ability to maneuver showing light signals of red-white-red combination on its mast.

Day Shapes

As per Rule 27 of COLREGs, a vessel restricted in her ability to maneuver shall display the following three shapes in a vertical line: 

  • the highest and lowest of the shapes shall be balls and
  • the middle one is a diamond
A dredger displaying a day shape of ball-diamond-ball on its mast indicating she is restricted in her ability to maneuver due to the nature of her work.

Sound Signals

The sound signal for all types of ships restricted in their ability to maneuver is one prolonged blast followed by two short blasts at intervals of not more than two minutes.

Vessels Constrained by Their Draft

A vessel is constrained by her draft when she cannot easily deviate or change course due to the limitations of the navigable waters around her.

Rule 28 of COLREGs has a bit longer, albeit standard definition than that, but that above is the gist of it.

Vessels constrained by their drafts always pay attention to their echo sounders to avoid running aground.

Light Signals

A vessel constrained by her draft must display three all-round red lights in a vertical line in addition to the lights described for a power-driven vessel.

You will likely see huge bulk carriers and tanker vessels display these light signals in narrow channels.

A tanker vessel showing three red lights in addition to its navigational lights indicating she is constrained by her draft.

Day Shapes

The day sign for a vessel constrained by her draft is a black cylinder hoisted where it can best be seen.

A ship showing a black cylinder day shape on her mast indicating she is constrained by her draft.

Sound Signals

The sound signal for a ship constrained by her draft is one prolonged blast followed by two short blasts at intervals of not more than two minutes.

Pilot Vessels on Pilotage Duties

A pilot vessel, also known as a pilot boat or pilot launch, is a ship that ferries maritime pilots to and from ships back to the pilot boat.

Rule 29 of COLREGs sets the standard lights and day signal required for a pilot boat.

Light Signals

A vessel engaged in pilotage duties shall exhibit two all-round lights, one above the other, the upper white and the lower red.

If the pilot launch is underway, it shall display the required lights for a power-driven vessel.

Light signals for pilot boats showing all-round white over green.

Day Shapes

Pilot vessels don’t have day shape combination similar to the ship above. However, they do display the “Hotel flag,” which signifies, “I have a pilot on board.”

A pilot boat underway displaying a Greek flag and the hotel flag indicating it has pilot on board.

Sound Signals

The sound signal for vessels engaged in pilotage duties is four short blasts, equivalent to a Morse Signal for the letter “H” or “Hotel.”

Vessels at Anchor

Rule 30 of the collision regulation specifies the standard lights and day shapes that anchored vessels must exhibit when anchored.

Note that a vessel dragging her anchor is not at anchor but considered underway.

Light Signals

After safely dropping the anchor, the ship must display her anchor lights which is a single all-round white light for vessels of less than 50 meters.

Ships 50 meters and above are required to have two all-round white lights where they can best be seen:

  • the fore part, an all-round white light;
  • at or near the stern and at a lower level than the light.
Ships at anchor showing anchor lights. The bigger one illuminates her deck.

Day Shapes

All vessels at anchor must display a single black ball, often called an anchor ball, where it can best be seen.

In most cases, many ships hoist the anchor ball on the forward part of the vessel.

A black ball hoisted on the forward part of the ship indicating the vessel is at anchor.

Sound Signals

Vessels at anchor during restricted visibility may ring the bell rapidly for about 5 seconds at intervals of not more than 1 minute.

For ships over 100 meters long, the bell shall be sounded on the fore part and the gong at the aft part.

Lastly, the anchored vessel must also sound one short, one prolonged and one short blast.

Vessel Aground

Rule 30 also specifies the lights to be displayed for vessels running aground.

Light Signals

A vessel aground must display the anchor lights prescribed for its length.

In addition, she must exhibit two red lights, one above the other, where it can best be seen.

Two vessels aground each showing two red lights in a vertical line. One has all-round anchor lights forward and aft while the other only has one all-round white light.

Day Shapes

The day shape of a vessel running aground is three black balls raised in a vertical line where it can best be seen.

You will appreciate the importance of lights and shapes as part of your navigational equipment, as properly identifying them plays a crucial role in marine navigation.

A huge bulk carrier aground near the shore. You can see three black balls on her mast.

Sound Signals

The sound signals for ships aground shall be the same as that of an anchored vessel.

In addition, she may give three separate and distinct strokes on the bell immediately before and after the rapid ringing of the bell.

Towing and Pushing Vessels

Towing and pushing ships are vessels specifically designed to assist other vessels in moving through waterways.

Rule 24 of COLREGs lays out many details and requirements for lights and shapes for ships engaged in towing or pushing.

Towing Vessels

Towing Vessels means any commercial vessel engaged in towing another vessel astern, alongside, or by pushing ahead.

Light Signals

A towing vessel shall display the following lights:

  • sidelights
  • a sternlight
  • a yellow towing light above the sternlight
  • two masthead lights in a vertical line if the length of two is LESS than 200 meters.
  • three masthead lights in a vertical line if the length of two is MORE than 200 meters.
  • If the length of the towing vessel is more than 50 meters, an additional masthead light aft.
Different light signals for towing vessels of different lengths.

A towing vessel can also display the lights prescribed for vessels restricted in her ability to maneuver if applicable.

Day Shapes

Towing vessels must display a black diamond shape where it can best be seen if the length of the tow is more than 200 meters.

Additionally, he can exhibit the day shape prescribed for a vessel restricted in her ability to maneuver.

An orange tugboat showing a diamond shape on its mast while towing a huge vessel with a blue hull.

Sound Signals

The sound signal of a towing vessel is one prolonged followed by two short blasts at intervals of not more than two minutes.

Pushing Vessels

Pushing vessels can either act as a composite unit or towing alongside.

Light Signals

A pushing vessel and the vessel being pushed act as a composite unit, they shall be regarded as a power-driven vessel and must follow the lights prescribed for power-driven vessels.

A pushing vessel not in a composite unit shall display the following lights:

  • sidelights
  • a sternlight
  • two masthead lights on top of each other.
  • if the length of the pushing vessel is more than 50 meters, an additional masthead light aft.
Towing vessels pushing ahead and alongside each showing navigational lights and light signals combinations.

Day Shapes

The object being towed alongside must display a black diamond shape where it can best be seen if the length of the tow is more than 200 meters.

Sound Signals

Just like vessels towing astern, pushing vessels must sound one prolonged followed by two short blasts at intervals of not more than two minutes.

May the winds be in your favor.

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