It used to be ecologically rich , and its brackish waters , fed by both rivers and sea , supported a healthy population of seals . It also provided an access point for migrating fish like salmon and sturgeon . As a result of the North Sea flood of 1953 the Haringvliet was closed off by the Haringvlietdam . The Haringvliet lost its estuarine characteristics and became a freshwater lake . 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
North Sea flood of 1953
North Sea flood of 1953
Haringvliet