What does the yellow square indicate when placed on a buoy?

The yellow square on a buoy designates a part of the Intracoastal Waterway (ICW). This marking is quite significant because it helps mariners identify key areas within the ICW, which is a vital route for vessels along the coast of the United States. The ICW provides safe navigation and access to ports and harbors by linking natural and man-made channels.

Understanding the role of this symbol is crucial for maintaining safe navigation, as it indicates specific regulatory zones or waters that are intended for particular uses. Recognizing these markers allows operators to comply with navigation rules and avoid potential hazards in busy waterway systems.

Other options may refer to other types of buoy markings or navigational information but do not accurately reflect what the yellow square indicates.