The Haringvliet is a large inlet of the North Sea, in the province of South Holland in the Netherlands.
The Haringvliet was formed as a result of the extensive flooding event of 1216, which breached the dunes of Voorne and created a deep saltwater inlet.
It used to be ecologically rich, and its brackish waters, fed by both rivers and sea, supported a healthy population of seals.
[5] Because of that, the seals are gone and migrating fish can only enter the Rhine-Meuse Delta through the busy and heavy industrialised Nieuwe Waterweg.
There are plans to permanently open a few of the Haringvliet sluices, to partly restore the ecosystem.