Sunrise on the Wadden Sea coast by Dick Hoogenboom

A number of rivers flowed into the Wadden Sea. The mouth widened into an estuary such as the Dollard, the Lauwerszee, the Middelzee and the Zuiderzee. The latter three have since been closed off. Completed in 1932, the Afsluitdijk has been part of the southern border of the Wadden Sea since that year. The Wadden Sea is interrupted by the Hindenburgdamm on the island of Sylt and the Rømødæming, the dam to Rømø.

The Wadden Sea area is of great natural value and is listed as a UNESCO World Heritage Site.The World Heritage Site covers more than 12,000 km², including the transition area to the North Sea (around 4,000 km²). The Wadden Islands of the Netherlands and Schleswig-Holstein (almost 700 km²) and the estuaries of the Ems, Außenjade, Weser and Elbe are largely excluded. However, these areas are largely covered by the Natura 2000 regime. The protection measures are coordinated by the International Wadden Sea Secretariat (CWSS) in Wilhelmshaven, in which the Netherlands, Germany and Denmark collaborate. Decisions are taken during triennial ministerial conferences, where the ministers concerned consult with each other. In addition, there are periodic scientific conferences and, between 2002 and 2023, there was a Wadden Sea Forum, in which civil society organisations and interest groups could make their voices heard.

The vulnerability of this Wadden Sea area was demonstrated by the MSC Zoë disaster on the night of 1 to 2 January 2019, when a large amount of plastic (pellets) and consumer products ended up in the sea. Thousands of volunteers helped to clean up the coastline. The exact consequences for the area are still being investigated.