Morecambe Bay on the North West coast of England covers an area of approximately 455 square kilometres. Around 1 billion cubic metres of water enters and leaves the Bay with every tide, covering an inter-tidal zone of approximately 340 square kilometres.  

The Duddon Estuary lies north of Morecambe Bay on the west Cumbrian coast. It is formed by the River Duddon and the smaller Kirkby Pool. It has a shoreline length of approximately 65km, a primary channel length of approximately 23km, and a core area of approximately 61 square kilometres.