Beacon

A beacon is a fixed aid to navigation built on the seabed, a rock, or the shore, as opposed to a floating buoy. It may be lit or unlit and carries the same IALA characters as its buoyed equivalent: a lateral, cardinal, isolated-danger, safe-water, or special function shown by color, topmark, and, if lit, light rhythm. Because it does not move with the tide or drag its mooring, a beacon gives a more reliable position than a buoy, so it is preferred for marking a fixed danger or a precise channel edge where structure can be founded. The chart abbreviation Bn marks it; a lit beacon is a minor light in the light list.