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