The Wadden Sea is shallow sea extending along the North Sea coasts of the Netherlands, Germany and Denmark. It includes the tidal channels, wetlands, mud flats, beaches, dunes, islands and offshore seas and is rich in biodiversity.
The Dutch part of the Wadden Sea is a World Heritage Site and lays between Den Helder and Groningen, in total covering a surface area of 2,550 km2 (~985 mi2).
Numerous plant and animal species including the harbour seal and grey seal live here. Around 8,000 seals in total are found in the Dutch Wadden Sea. This includes more than 2,100 grey seals and they can often be spotted on various banks either to rest or give birth. It is also considered one of the most important areas for migratory birds in the world and 6.1 million birds can often be present here at the same time.
On average, 10-12 million pass through here each year and for millions of these birds, it is an essential stopover or resting place. An abundance of many types of fish can be found here. For instance fish such as plaice, sole, herring and sprat, use the Wadden Sea as a nursery and countless young fish grow up here, migrating later on to the North Sea.
Aside from its importance to amateur and professional natural historians alike, the Wadden Sea provides plenty of opportunities for activities. The five Dutch Wadden Sea Islands are highly popular holiday spots. Each has its own character, but all have outstanding natural beauty; and beaches for leisure and sporting activities. Mudflat hiking, crossing the watershed of mudflats at low tides, is a highly popular activity in the Netherlands and there are recognised routes from the mainland to at least three of the five islands.