The changing shoreline on Martha's Vineyard variously fascinates, startles or horrifies people, depending on where they live or own property. The strongest supporting images of erosion are provided by destruction of buildings located at the water's edge, such as lighthouses and Worlds War II military bunkers. Among the latter, a concrete bunker (part of the Katama Naval Air Station target track) once 180 feet from the shore at South Beach in Edgartown was last seen far offshore, drowned in the surf. The associated rate of shoreline retreat comes to about 12 feet per year.