Boating Basics: On the Water

Nighttime Navigation

You should always be on the lookout for the lights of other vessels when boating at night. Several types of lights serve as navigational aids at night. They are:

Types of Nighttime Navigational Lights

Illustrations

Sidelights: These red and green lights are called sidelights (also called combination lights) because they are visible to another vessel approaching from the side or head-on. The red light indicates a vessel’s port (left) side; the green indicates a vessel’s starboard (right) side.

Sternlight: This white light is seen from behind the vessel.

Masthead Light: This white light shines forward and to both sides and is required on all power-driven vessels. A masthead light must be displayed by all vessels when under engine power. The absence of this light indicates a sailboat under sail.

All-Round White Light: On power-driven vessels less than 39.4 feet in length, this light may be used to combine a masthead light and sternlight into a single white light that can be seen by other vessels from any direction. This light serves as an anchor light when sidelights are extinguished.

Sailboat showing sidelights, masthead light, and sternlight Powerboat showing all-round white light and red and green sidelights

Encountering Vessels at Night

Encountering Vessels at Night - What the Lights Mean	Illustrations of Lights
A green and a white light: When you see a green and a white light, you are the stand-on vessel. However, remain alert in case the other vessel operator does not see you or does not know the navigation rules.	Movie: See the action!
Only a white light: When you see only a white light, you are overtaking another vessel or it is anchored. It is the stand-on vessel whether it is underway or anchored. You may go around it on either side.	Movie: See the action!
A red and a white light: When you see a red and a white light, you must give way to the other vessel! Slow down and allow the vessel to pass, or you may turn to the right and pass behind the other vessel.	Movie: See the action!
A red, a green and and a white light: When you see a red, a green, and a white light, you are approaching another power-driven vessel head-on and both vessels must give way.	Movie: See the action!
Encountering Sailing Vessels at Night - What the Lights Mean	Illustrations of Lights
A red and a green but no white light: When you see a red and a green light but no white light, you are approaching a sailing vessel head-on and you must give way.	Movie: See the action!
When you see only a red light or only a green light, you may be approaching a sailboat under sail and you must give way. A sailboat under sail is always the stand-on vessel!	See only a red light... Movie: See the action!
	See only a green light... Movie: See the action!

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Online boating safety handbook last modified: July 27, 2009
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