International Maritime Signals: Lights, Shapes, and Sound Codes

Maneuvering and Warning Sound Signals (Vessels in Sight)

These signals use short blasts (o, approximately 1 second) and prolonged blasts (__, 4–6 seconds).

• o: I am altering my course to starboard.
• oo: I am altering my course to port.
• ooo: I am operating astern propulsion (giving back).
• ooooo: Danger signal. I do not understand your intentions or actions.
• __ __ o: I intend to overtake you on your starboard side.
• __ __ oo: I intend to overtake you on your port side.
• __ o __ o: I agree with your proposed overtaking maneuver.
• __: Prolonged blast used as a warning signal when approaching a bend or leaving a berth.

Acoustic Signals in Reduced Visibility (Fog Signals)

These signals are sounded at intervals not exceeding two minutes.

• __: Power-driven vessel making way through the water.
• __ __: Power-driven vessel underway but stopped and not making way.
• __ o o: (Prolonged, two short blasts) Signal used by:
  • Vessel not under command (NUC).
  • Vessel restricted in ability to maneuver (RAM).
  • Vessel constrained by her draft (CBD).
  • Sailing vessel.
  • Fishing vessel.
  • Vessel engaged in towing or pushing.
• __ o o o: (Prolonged, three short blasts) Vessel being towed, or the last vessel in a tow (if manned).
• o __ o: (Short, prolonged, short) Signal used by a vessel at anchor to warn an approaching vessel of her position.
• o o o o: (Four short blasts) Identifying signal for a Pilot vessel.

Day Shapes

Vessels display specific black shapes during daylight hours to indicate their status or operational constraints.

• Vessel Not Under Command (NUC): Two black balls (vertical).
• Vessel Restricted in Ability to Maneuver (RAM): Ball, Diamond, Ball (vertical).
• Vessel Constrained by Her Draft (CBD): One black cylinder.
• Vessel Aground: Three black balls (vertical).
• Vessel At Anchor: One black ball.
• Vessel Engaged in Trawling: Two cones with apexes together (hourglass shape).
• Vessel Under Sail and Power: One cone, apex downwards (inverted triangle).
• Vessel Engaged in Minesweeping: Three balls (one forward, one on each yardarm).
• Vessel Being Towed (if tow exceeds 200m): One diamond shape.

Night Navigation Lights

Towing and Pushing Operations

• Towing Vessel (Tow less than 200m): Two masthead lights (vertical), sidelights, stern light, and a yellow towing light (above the stern light).
• Towing Vessel (Tow 200m or more): Three masthead lights (vertical), sidelights, stern light, and a yellow towing light.
• Vessel Being Towed: Sidelights and a stern light.

Vessels with Operational Constraints

• Vessel Not Under Command (NUC): Sidelights, stern light, and two all-round red lights (vertical).
• Vessel Restricted in Ability to Maneuver (RAM): Sidelights, stern light, masthead light(s), and three all-round lights (Red-White-Red, vertical).
  • Note: If also towing, the RAM lights are displayed in addition to the required towing lights.
• Vessel Constrained by Her Draft (CBD): Sidelights, stern light, masthead light(s), and three all-round red lights (vertical).

Fishing and Sailing Vessels

• Vessel Engaged in Trawling: Sidelights, stern light, and two all-round lights (Green over White, vertical).
  • If the vessel is over 50m, it must also show an additional masthead light aft of the G/W lights.
• Vessel Engaged in Fishing (Other than Trawling): Sidelights, stern light, and two all-round lights (Red over White, vertical).
• Sailing Vessels: Sidelights and a stern light.
  • Optional: Two all-round lights (Red over Green, vertical) at the masthead.
  • Vessels less than 20m may combine these lights into a single lantern.
  • Vessels less than 7m can use a white torch or lantern if necessary.

Stationary and Pilot Vessels

• Pilot Vessel: White over Red all-round lights (vertical). When underway, also shows sidelights and a stern light.
• Vessel At Anchor:
  • Less than 50m: One all-round white light forward.
  • 50m or more: One all-round white light forward and one aft.
  • 100m or more: Must also illuminate the decks.
• Vessel Aground: Anchor lights plus two all-round red lights (vertical).