Actually there are several known examples of rapid shoreline change. Here are 10:
http://listverse.com/2013/08/05/10-lesser-known-mysterious-underwater-cities/
and 5 more:
http://www.earthporm.com/5-mind-blowing-underwater-cities/
most are due to earthquakes, major storms, or tsunami (I guess that could be earthquake related). Though some like the one in the Denmark region took a number of happenings over time. God moves nature quick some times.