The Mersey Mouth is the dynamic tidal estuary where the River Mersey meets the Irish Sea, forming a significant coastal water body off the coast of Lancashire. This area is characterized by its powerful tidal vigour, which historically provided an enviable anchorage and continues to shape the fishing environment. The estuary's mouth stretches from the Crosby and Hightown areas on the northern shore to New Brighton on the Wirral peninsula, creating a broad, sandy and muddy intertidal zone influenced by the river's outflow and the sea's tidal forces.