Complete reference index
Read each signal’s meaning, context and limitations. Use the interactive cards above for visual or listening practice.
Manoeuvring light: starboard alteration
“I am altering my course to starboard.” With vessels in sight, this may supplement the one-short-blast announcement.
An optional all-round white light gives 1 flash, supplementing the corresponding whistle signal. A white light flashes in groups of 1, with a long dark interval between groups. Each flash is about 1 second, with about 1 second between flashes and at least 10 seconds between successive groups. This optional light supplements the whistle; it is not a steady status light. The prescribed light is visible at least 5 miles; screen size does not represent range.
Source: Rule 34(b) · International
Manoeuvring light: port alteration
“I am altering my course to port.” With vessels in sight, this may supplement the two-short-blast announcement.
An optional all-round white light gives 2 flashes, supplementing the corresponding whistle signal. A white light flashes in groups of 2, with a long dark interval between groups. Each flash is about 1 second, with about 1 second between flashes and at least 10 seconds between successive groups. This optional light supplements the whistle; it is not a steady status light. The prescribed light is visible at least 5 miles; screen size does not represent range.
Source: Rule 34(b) · International
Manoeuvring light: astern propulsion
“I am operating astern propulsion.” This may supplement three short blasts; it does not prove backward movement.
An optional all-round white light gives 3 flashes, supplementing the corresponding whistle signal. A white light flashes in groups of 3, with a long dark interval between groups. Each flash is about 1 second, with about 1 second between flashes and at least 10 seconds between successive groups. This optional light supplements the whistle; it is not a steady status light. The prescribed light is visible at least 5 miles; screen size does not represent range.
Source: Rule 34(b) · International
Diving: simplified red–white–red display
When vessel size makes all the Rule 27(d) diving lights and shapes impracticable, show these lights and a rigid Alfa replica.
Three all-round lights vertically: red, white, red. The daytime replica must be at least 1 m high and visible all round. A vertical red–white–red stack. Red–white–red also identifies other restricted work; the lights alone do not prove a diver is down. This is the specific size/impracticability provision, not a universal substitute for the complete underwater-work display.
Source: Rule 27(e)
Non-trawling fishing: outlying gear
Non-trawling fishing gear extends more than 150 m horizontally from the vessel.
Red-over-white status lights, plus an all-round white light in the direction of the gear. This example is making way and adds sidelights and sternlight. Red over white, with an additional white light towards the outlying gear and ordinary sector lights. The extra light is not a safe-passing invitation or an ordinary power masthead. The underlying fishing day shape is also required by day.
Source: Rule 26(c)(ii)
Severely restricted towing: long tow
A tow over 200 m whose operation severely restricts tug and tow from deviating combines towing and restricted-manoeuvrability displays.
Three white mastheads for the long tow, red–white–red all-round status lights, sidelights, sternlight and yellow towing light. A white towing stack alongside a red–white–red status stack, plus sector navigation and towing lights. Tow length alone does not establish severely restricted manoeuvrability. The corresponding daytime combination is ball–diamond–ball plus the long-tow diamond.
Source: Rules 27(c) and 24(a)
SOS distress by flashing light
Distress and need of assistance, signalled as the Morse SOS group.
Three dots, three dashes, three dots, sent as one Morse group. A white light flashes three brief, three longer, then three brief pulses. Morse dashes are three dot units, not the 4–6 second COLREG prolonged-blast timing. This sample uses a 1-second dot and an illustrative repeat pause. Reserved for distress and need of assistance.
Source: Rule 37 and Annex IV 1(d)
Power-driven vessel under 50 m
A power-driven vessel underway, using the standard masthead, sidelights and sternlight arrangement.
One white masthead light; red port and green starboard sidelights; white sternlight. A white forward-facing light above red and green sidelights; a separate white aft-facing light. This is the standard arrangement, not every permitted small-boat alternative. Masthead is a 225° sector light, not an all-round light; sidelights are 112.5° each and the sternlight is 135°.
Source: Rule 23(a)
Power-driven vessel 50 m or longer
A power-driven vessel underway with the additional after masthead light required from 50 m.
Two white masthead lights; the after one is abaft and higher. Sidelights and sternlight as usual. Two white forward-facing lights at different fore-and-aft positions and heights, plus sector navigation lights. The lights are not a vertical towing stack. Vessels under 50 m may also show a second masthead, so two mastheads do not prove the vessel’s exact length.
Source: Rule 23(a)(ii)
Power-driven vessel under 12 m: alternative
A power-driven vessel under 12 m may use this permitted alternative arrangement.
An all-round white light and red/green sidelights. An all-round white light and two sidelights. The all-round white remains visible astern; do not add a separate sternlight to this illustrated alternative. A single white light alone is not enough to identify a small powerboat.
Source: Rule 23(d)(i)
Sailing vessel underway
A vessel under sail and not propelled by machinery shows sidelights and a sternlight.
Red port, green starboard and a white sternlight; no power-vessel masthead light. Sector sidelights and a white aft-facing light, without a white masthead. Under machinery propulsion, a yacht uses power-driven lights even if its sails remain set. This deck’s hull silhouette is only context; identify the actual lights and aspect.
Source: Rule 25(a)
Sailing vessel under 20 m: tricolour lantern
A sailing vessel under 20 m may combine its sidelights and sternlight in one lantern at or near the mast top.
One fitting with red port, green starboard and white stern sectors. Three sector colours located in a single mast-top lantern. You cannot see all three sectors from one viewing position. Do not combine this lantern with the optional red-over-green sailing lights, and do not use it as a substitute for power-driven lights while motoring.
Source: Rule 25(b)
Sailing vessel: optional red over green
A sailing vessel may add red-over-green all-round lights near the mast top to its ordinary deck-level sidelights and sternlight.
All-round red above green, plus ordinary sidelights and sternlight. A vertical red-over-green pair with separate navigation sector lights. These are optional additional sailing lights. They must not be shown together with a masthead tricolour lantern. When the engine propels the yacht, use the applicable power-driven arrangement.
Source: Rule 25(c)
At anchor: vessel under 50 m
A vessel under 50 m may show one all-round white light where it can best be seen at anchor.
One all-round white light. One steady white all-round light. One white light can also be a sternlight or a small-vessel arrangement; context matters. Under-7 m anchor exemptions are limited to places away from normal navigation, channels, fairways and anchorages.
Source: Rule 30(b), (e)
At anchor: fore and aft lights
The standard anchor arrangement has a white light forward and a lower white light at or near the stern.
Two all-round white lights, fore higher than aft. Two steady white all-round lights, at different positions and levels. Do not confuse these all-round lights with the 225° mastheads of a vessel underway. Vessels 100 m or longer must also illuminate their decks; deck illumination is not drawn here.
Source: Rule 30(a), (c)
Not under command: not making way
Exceptional circumstances prevent the vessel from manoeuvring as required by the Rules.
Two all-round red lights vertically. Two steady all-round red lights in a vertical line. This card is not making way through the water. A not-under-command vessel making way adds sidelights and a sternlight. Aground vessels also show two reds, but additionally have their anchor lights.
Source: Rule 27(a)
Not under command: making way
A not-under-command vessel making way through the water adds sidelights and a sternlight to its two reds.
Red over red, plus sidelights and sternlight; no ordinary power masthead in this prescribed display. Two red all-round lights with red/green sector sidelights and a white sternlight. Underway and making way are not synonyms. A drifting vessel may be underway without making way through the water. Do not assign stand-on duties from a status mnemonic alone.
Source: Rule 27(a)(iii)
Restricted manoeuvrability: not making way
The nature of the vessel’s work restricts its ability to manoeuvre.
Three all-round lights vertically: red, white, red. A steady red–white–red vertical stack. This card illustrates a vessel not making way and not at anchor. Making way adds the applicable masthead, sidelights and sternlight; at anchor it normally adds anchor signals, with particular provisions for dredging and underwater work.
Source: Rule 27(b)
Restricted manoeuvrability: making way
A working vessel restricted in ability to manoeuvre, making way through the water.
Red–white–red all-round, plus a masthead, sidelights and sternlight in this under-50 m example. A red–white–red stack with an additional white forward light and navigation sector lights. Read the whole display. Vessels 50 m or longer use the additional after masthead as applicable; dredging, diving and mineclearance have special provisions.
Source: Rule 27(b)(iii)
Constrained by draught
A power-driven vessel severely restricted by its draught relative to available depth and width may show three red all-round lights.
Three reds vertically in addition to power-driven lights; this example uses two mastheads. A steady red–red–red stack with power-vessel sector lights. Optional under the International Rule; not every large ship qualifies. Three reds alone are not the complete normal display, and the inland US rules do not have the same constrained-by-draught provision.
Source: Rule 28 · International
Trawling: under 50 m, making way
A vessel dragging a dredge net or other fishing apparatus through the water.
All-round green over white; when making way, sidelights and sternlight. Green above white, with navigation sector lights. An additional masthead abaft and higher than the green is required from 50 m, and optional below 50 m. This card omits that optional masthead. Without making way, the sidelights and sternlight are not added.
Source: Rule 26(b)
Fishing other than trawling: making way
A vessel engaged in qualifying fishing other than trawling.
All-round red over white; sidelights and sternlight when making way. Red above white, with navigation sector lights. Gear extending more than 150 m adds a white all-round light towards the gear. Do not confuse red-over-white fishing with white-over-red pilotage; ordinary trolling that does not restrict manoeuvrability is not this status.
Source: Rule 26(c)
Pilot vessel on duty: underway
A vessel engaged on pilotage duty, underway.
All-round white over red, plus sidelights and sternlight when underway. White above red, with navigation sector lights. The order is the reverse of fishing other than trawling. At anchor, a pilot vessel adds the anchor lights instead; when not on pilotage duty it uses the normal display for a similar vessel.
Source: Rule 29(a)
Aground: 12 m to under 50 m example
The vessel is aground and shows its anchor light plus two red all-round lights.
Two reds vertically and an all-round white anchor light. A red-over-red pair with a separate white all-round light. Two reds alone can be not under command. This example uses the single-anchor-light option for under 50 m; larger vessels use the appropriate fore/aft anchor lights. Vessels under 12 m are exempt from the extra aground reds.
Source: Rule 30(d), (f)
Towing astern: tow not exceeding 200 m
A power-driven vessel towing astern, illustrated with a towing vessel under 50 m.
Two vertical white mastheads, sidelights, sternlight, and yellow towing light above the sternlight. Two white forward lights in a vertical stack; aft, yellow above white. Tow length includes the distance from the tug’s stern to the after end of the tow. The aft yellow is a 135° towing light, not an all-round yellow. Additional mastheads apply to larger towing vessels as prescribed.
Source: Rule 24(a)
Towing astern: tow longer than 200 m
A power-driven vessel towing astern with a tow exceeding 200 m, using an under-50 m tug example.
Three white mastheads vertically, sidelights, sternlight and yellow towing light above it. Three white forward lights vertically; aft, yellow above white. The tow is not just the line length. Do not confuse three forward-facing whites with the all-round red–white–red restricted-work stack; colour and sectors matter.
Source: Rule 24(a)
Dredger or underwater work: obstruction
Restricted underwater work: two reds indicate the obstructed side; two greens indicate the side on which another vessel may pass.
Central red–white–red; two reds on one side and two greens on the other. Not making way in this example. A red–white–red central stack with a red pair and a green pair to its sides. These side indicators are all-round work-status lights, not ordinary port/starboard sidelights. Passing permission still requires safe clearance and depth. The designated side can change with the operation.
Source: Rule 27(d)
Mineclearance vessel underway
The three green all-round lights warn that approaching within 1,000 m is dangerous.
One green near the foremast head and one at each fore-yard end, plus normal power-vessel lights. Three widely spaced green all-round lights, one above the other two. Not a vertical green stack, and not the green pair used on a dredger’s passing side. At anchor, the vessel uses the corresponding anchor signals with the mineclearance display.
Source: Rule 27(f)
Air-cushion vessel in non-displacement mode
An air-cushion vessel operating in non-displacement mode adds an all-round flashing yellow light.
Power-driven lights plus a flashing all-round yellow light. A flashing yellow all-round light with ordinary power-vessel lights. Do not confuse an all-round flashing yellow with the steady, aft-sector yellow towing light. This is a vessel signal, not a buoy light identification.
Source: Rule 23(b)
Wing-in-ground craft taking off, landing or flying near the surface
A WIG craft in these operating conditions adds a high-intensity all-round flashing red light to its power-driven lights.
Power-driven lights plus a high-intensity flashing all-round red light. A flashing red all-round light with ordinary power-vessel lights. The screen illustrates flashing but not the prescribed real-world intensity. Do not confuse a single flashing red with two steady reds for not under command.
Source: Rule 23(c)