What is meant by the term "air gap" in relation to Aids to Navigation?

The term "air gap" refers to the space allowing buoy visibility. This is crucial for mariners navigating in a waterway, as it helps ensure that a buoy can be seen from a distance, providing necessary guidance and warnings for safe passage. A sufficient air gap ensures that buoys do not become submerged under various water levels or obscured by obstacles, thus maintaining their efficacy as navigational aids.

While other aspects of buoy placement, such as distance between buoys, the height of a buoy above water, and clearance required for vessels are important, they do not define the term "air gap." Each of those elements relates to different navigational concerns, but the visibility and prominence of a buoy in relation to the water's surface is specifically tied to the concept of air gap. Keeping buoys at an appropriate height above the water ensures they remain noticeable and serve their intended purpose effectively, which is vital for navigation safety.