In 1362, there was the great flood that changed the coastline of the North of Germany forever. A whole town was lost (Rungholt) and lies forever under the waterlevel close to where now the Hallig (Hallig is the German name for an island which is completely covered by water at srpingtides that is several times a year) Suedfall lies.

Here's an old German poem about it (for those who can read Germen):

Trutz, Blanke Hans

Trutz is an out of use noun and means 'withstanding'
'Blanke Hans' is the sea.

Wolfgang