Between the ship from which the picture was taken and the Hallig you see there is a sunken medieval city. One day (January 16, 1362) a storm came and took the land away. The whole city just disappeared under the North Sea. The existence of the city has been thought a legend for a very long time.  However, locals kept on finding objects and spots in the Wadden Sea throughout the past decades. Nowadays, there is a solid scientific evidence for the existence of a prosperous center of trade which is covered by tons of mud. The name of the place was Rundholt. North Friesland. My favorite kind of muddness. 2010.