The Wash is a shallow natural rectangular bay and multiple estuary on the east coast of England in the United Kingdom.

The Wash makes a large indentation in the coastline of Eastern England that separates Lincolnshire from the curved coast of East Anglia.

The eastern coast of the Wash is entirely within Norfolk, and initially extends from the mouth of the River Great Ouse just north of the town of King's Lynn north eastwards towards the small village of Wolferton close to the Sandringham estate before heading northwards from Snettisham to the low lands of Heacham, the town of Hunstanton, and the village of Old Hunstanton, before reaching its northern extremity at Gore Point near Holme-next-the-Sea, where the Norfolk coast turns eastwards.

Inland from the Wash the land is flat, low-lying and often marshy: these are the Fens of Lincolnshire, Cambridgeshire and Norfolk.

This effect, which typically happens in the shallow areas around beaches and often only in pockets of water, is exaggerated by the large sheltered tidal reach.

The Wash is made up of extensive salt marshes, major inter-tidal banks of sand and mud, shallow waters and deep channels.

This is an example of the recent exploration of the possibilities of sustainable coastal management by adopting soft engineering techniques, rather than with dykes and drainage.

The gravel pits (lagoons) found at Snettisham RSPB reserve are an important roost for waders at high tide.

The partly confined nature of the Wash habitats, combined with ample tidal flows, allows shellfish to breed, especially shrimp, cockles and mussels.

Before the 12th century, when drainage and embankment efforts led by monks began to separate the land from the estuarine mudflats, the Wash was a tidal part of the Fens that reached as far as Cambridge and Peterborough.

By then, documents began to refer to the Waashe or Wysche, but only for the tidal sands and shoals of the rivers Welland and Nene.

Sixteenth-century scholars identified the Wash as the Æstuarium Metuonis ("The Reaping/Mowing/Cutting-Off Estuary") mentioned by Ptolemy in Roman times.

Inspired by Camden's account, William Shakespeare mentioned the Lincolne-Washes in his stage play King John (1616).

In the 1970s, two large circular banks were built in the Terrington Marsh area of the Wash, as part of an abortive attempt to turn the entire estuary into a fresh water reservoir.

The plan failed, not least because the banks were built using mud dredged from the salt marsh, which salinated fresh water stored there.

From 13th century the market town and seaport of Bishop's Lynn became the first member trading depot (Kontor) in the Kingdom of England of the Hanseatic League of ports.

During the 14th century, Lynn ranked as the most important port in England, when sea trade with Europe was dominated by the League.

[3] According to contemporary reports, John travelled from Spalding, Lincolnshire, to Bishop's Lynn, Norfolk, but was taken ill and decided to return.

However, the treasure hunter and researcher Alan Marshall has proven from data supplied him by the Royal Greenwich Observatory and by the Bidston Observatory in Birkenhead that the tide had actually been going out, and by further studying the lay of the now reclaimed land, he ascertained that the cause had been a reverse tidal surge, whereby the outgoing tide suddenly sped up at a certain point.

[18] The four most distinctive man-made landmarks that can be seen from the bay are: The Outer Trial Bank, a remnant of a 1970s experiment, lies some two miles (three kilometres) off the Lincolnshire coast near the mouth of the River Nene.

The most notable nature feature is Hunstanton Cliffs, comprising strata of orange, red and white chalk.