Which Navigation Lights Must a Sailboat Show at Night Under Sail

Quick Answer

A sailboat operating under sail at night must show sidelights (red to port, green to starboard), a sternlight (white 135° sector), and, when making way, a combined masthead light of red over green over white in a vertical line with an all-around white light beneath. When not making way (aground or at anchor), replace the masthead light with an all-around white light. These requirements stem from the International Regulations for Preventing Collisions at Sea (COLREGs) and apply to all vessels under sail, with or without auxiliary propulsion in use.

The International Regulations for Preventing Collisions at Sea (COLREGs), Annex II and Rule 20, define lighting based on vessel status and operational mode rather than size. The status and light configuration categories most relevant to sailboats at night are:

Underway and making way: showing lights to indicate direction of hull and progress through the water.
Underway but not making way: for example, a sailboat drifting in calm conditions; some lights are altered relative to making way.
At anchor: specific anchor lights replace combination lights used while underway.
Aground: treated distinctly in the rules and requires lights suitable for grounding circumstances.

Key constants to plan for include the required visibility ranges measured in nautical miles and the horizontal and vertical arcs over which lights must be visible. Color, sectors, shielding, and mounting height determine whether another vessel’s crew can correctly interpret your status and movements.

Light Color and Sectors Defined for Sail Under Sail

Sidelights and Their Purposes

Sidelights are the red light displayed to port and the green light displayed to starboard. They must be visible from right ahead to 22.5° abaft the beam on each side. Their primary purpose is to indicate which side of the vessel offers the best opportunity to pass, and a crossing situation is taking place when another vessel is within the combined sector from ahead to abaft the beam.

Sternlight Characteristics and Placement

The sternlight is a white light covering the aft 135° arc. It ensures vessels approaching from astern can recognize that a vessel is underway and where the stern lies relative to your hull. Proper placement and aftward shielding prevent stray light from obscuring the red and green sidelights and confusing nearby traffic.

For a sailboat under sail and making way, the single masthead light permitted is red over green over white. Horizontal arcs are critical: red extends 112.5° to port, green 112.5° to starboard, and white ahead. When combined with an all-around white light mounted below, the arrangement clearly indicates power conditions. The second arrangement is necessary when the overall height exceeds limits for a single-triangle fixture.

Status-Based Light Configurations in Detail

Underway and Making Way Under Sail

When your sailboat is moving forward under sail alone, display:

Sidelights: red to port, green to starboard.
Sternlight: white, 135° visible from astern.
Masthead light: red over green over white (or a combined fixture) plus an all-around white light beneath, both in a vertical line.

These lights elicit a clear crossing or overtaking response from other vessels and keep your status as a power-driven vessel by sail unmistakable. The red-over-green-over-white sequence is specifically reserved for sailboats under sail making way at sea or in narrow channels where interpretation matters.

Underway but Not Making Way

If your sail is set but you are not moving through the water, for example becalmed or drifting while under sail, display:

Sidelights and sternlight as when making way, since you are still underway.
Replace the combined masthead light with an all-around white light in place of the red-over-green-over-white arrangement.

Although some crews may debate the exact interpretation of sail set versus propulsion, the COLREG guidance favors treating the vessel as underway so long as there is continuing forward movement or potential movement under sail. The all-around white light minimizes misinterpretation by removing clear masthead directionality while preserving status as underway.

At Anchor

At anchor under sail, a sailboat should show:

An all-around white light where it can best be seen, typically at the masthead.
In many regions, additional illumination of the work deck is permitted or required, but the anchor light is defined by its white all-around character and placement.

Sidelights and sternlight are not required when anchored. If the vessel is also making way under auxiliary power while at anchor, additional status lights may apply, so confirm local practices and any special regulations for your class of vessel.

Aground

If your sailboat is aground, display two all-around red lights in a vertical line where they can best be seen. These indicate grounding to approaching traffic. If the vessel is also at anchor while aground, follow whichever set of rules prescribes the higher level of visibility, typically the grounding lights to maximize conspicuity.

Sailboats under sail have two recognized options for displaying the masthead light combination. Option one uses a single lantern showing red over green over white, which is simple and low-profile. Option two splits the colors across two or three separate lanterns, with an all-around white light mounted below the red-over-green section. Height, visibility, and obstruction from rigging guide which option a skipper selects. Both must conform to the defined color sequence and minimum candlepower to satisfy inspection and nighttime recognition requirements.

Summary Table of Lights for a Sailboat Operating Under Sail at Night

Status	Required Lights (Under Sail)	Masthead Light Type	Notes
Making way	Sidelights, sternlight	Red over green over white + all-around white below	Shows direction of hull and motion through water
Underway, not making way (e.g., drifting)	Sidelights, sternlight	All-around white (replaces red-over-green-over-white)	Vessel is underway but speed over ground is minimal
At anchor	All-around white light	All-around white at or near masthead	Sidelights and sternlight omitted
Aground	Two all-around red lights vertical	N/A	Maximum conspicuity for grounding situation

Practical Recommendations for Sailors

Verify that sidelights and sternlight are unobstructed and properly shielded to avoid stray glow that can hide sector limits.
Confirm the masthead fixture or combination meets minimum candlepower and arc requirements for your vessel’s length.
When in doubt between making way and not making way, err toward the configuration that communicates motion and heading clearly.
Keep spare bulbs and test fixtures before night passages, especially if relying on combined lanterns.
Supplement navigation lights with reflective tape or contrast where legally allowed to enhance visibility.

Regulatory Context and Inspections

Navigation light requirements stem from the International Regulations for Preventing Collisions at Sea (COLREGs). Flag state and classification society rules determine specific candlepower, mounting height, and arc tolerances during certification surveys and annual inspections. Owners and operators should retain copies of relevant certificates and understand local enforcement expectations, particularly when operating internationally or in congested waters where stricter municipal rules may apply.

Conclusion

A sailboat operating under sail at night should always show red and green sidelights and a white sternlight. When making way, it must additionally show red over green over white at the masthead, accompanied by an all-around white light below. When not making way, replace the combined masthead with a single all-around white light; when anchored, show only an all-around white light; and when aground, show two vertical all-around red lights. Correct interpretation of these rules reduces ambiguity at night and supports safe, predictable behavior among all vessel traffic.