The Wash is the square-mouthed estuary in East Anglia on the east coast of England, "where Norfolk meets Lincolnshire". It is the largest estuary in the United Kingdom. It is fed by the Rivers Witham, Welland, Nene and Great Ouse.
The Wash is a Special Protection Area (SPA) under European Union legislation. It is made up of very extensive saltmarshes, major intertidal banks of sand and mud, shallow waters and deep channels. The sea-wall at Freiston has been breached in three places to increase the saltmarsh area, to provide an extra habitat for birds and also as a natural flood prevention measure.
On the eastern side of the Wash, one finds low chalk cliffs at Hunstanton, and gravel pits (lagoons) at RSPB Snettisham which are an important roost for waders at high tide. This SPA borders onto the North Norfolk Coast Special Protection Area.
To the north, it borders onto Gibraltar Point Special Protection Area.
The sheltered nature of the Wash allows shellfish to breed, especially shrimps, cockles and mussels. Some waterbirds, e.g. oystercatchers, feed on shellfish. It is also an important breeding area for terns, and a feeding area for marsh harriers. Migrating birds, such as geese, ducks and wading birds, come to The Wash in huge numbers to spend the winter.
The most famous incident associated with the Wash is the loss of King John's royal treasure. According to contemporary chronicles, John was travelling from Spalding in Lincolnshire to King's Lynn in Norfolk, but unwisely sent his baggage train, including his crown jewels, along the coast road, which would only have been passable at certain times of day. The horse-drawn carts moved too slowly for the incoming tide, and many were lost. The present-day location is supposed to be somewhere near Sutton Bridge, on the River Nene.
The Boston Stump, a Lincolnshire landmark, can be clearly seen from the other side of the Wash.