The Wash is the largest bay in England. Roughly square in shape, 30 km to a side, coming off the North Sea south-eastward, forming the division between the counties of Lincolnshire and Norfolk.
The rivers Witham, Welland, Nene, and Great Ouse flow into it. All the country they drain before The Wash is very flat and fenny. It is perfect country for birds and birdwatchers but pretty depressing for human beings. ("Whilst some would refer to the area as bleak, windswept and monotonous, the remoteness and openness of the intertidal marshes seen against the setting of the agricultural hinterland together with the vast skies, sea smells and above all the teeming bird life combine to form a landscape of rare quality." -- www.wildfowling.com -- Well they would say that, wouldn't they?)
Legend says that King John (1199-1216) lost the Crown Jewels in the Wash, as part of his baggage train.