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cardinal marks 
Buoys of standardized colors, topmarks and lights whose placement alone or in a pattern corresponds to the divisions of a compass.
North
The north cardinal mark is composed of two topmarks with both tips pointing upward.
white light
White flashing light whose flash pattern serves as a cardinal mark at night.
Northwest
West
The west cardinal mark is composed of two topmarks placed tip to tip.
Southwest
safest water
Navigable water is deep enough that it is safe to proceed.
South
The south cardinal mark is composed of two topmarks with both tips pointing downward.
danger
Buoys signal shallow waters, a submerged object or an object posing a hazard to a boat or a ship.
Southeast
East
The east cardinal mark is composed of two topmarks placed base to base.
Northeast
topmark
Metal cone-shaped part atop a buoy that serves as a navigation aid during the day; its position signifies various meanings.
