In geologic terms, lakes are short-lived features. As soon as a lake basin forms, internal and external forces begin a process of change that leads to its eventual extinction. Wave action is one obvious force.
Waves wear away exposed points and transport beach materials to form bars cutting off bays.
One can sit on the bank of a reservoir like Lake Oroville, California, on a windy day and watch points being eroded and silt-laden tongues of water moving across the bays. Eagle Lake, California, has some of its history written in its outline. Eagle Lake is old, perhaps 100,000 years. Wave action smoothed its outline then violent geologic processes re-roughened portions of it but the relentless waves keep working. The oldest shoreline is apparent in the smooth contour of portions of the North and Middle Basins but faults long ago raised huge points of land between North and Middle Basin.