The Old Dock, originally known as Thomas Steers' dock, was the world's first commercial wet dock. The 3+1⁄2 acres (1.4 ha) dock was built on the River Mersey in Liverpool, England, starting in 1710 and completed in 1716. A natural tidal pool off the River Mersey, which probably gave its name to Liverpool centuries earlier, was partially filled and locked in from the river with quay walls erected.

A floating dock, floating harbour or wet dock is a dock alongside a tidal waterway which maintains a 'constant' level, despite the changing tides.