I received a postcard today from the Netherlands.
The West Frisian Islands or Wadden Islands (called De Waddeneilanden in Dutch) are a chain of islands in the North Sea, north of Netherlands and Germany and west of Denmark.
Between the islands and the mainland is the Wadden Sea, which at low tide is mostly dry.
The islands are inhabited by about 81,300 people. The largest island is the Dutch Texel, followed by the Danish Rømø and German Sylt. Sylt has about 21,000 inhabitants and is the most populous island.
Wikipedia - Waddeneilanden
Wikipedia - West Frisian Islands
The sender of this postcard wrote that when it is low tide, it is possible to walk to the islands from the mainland...called wad-hiking. That's what the people pictured on the postcard are doing!