Cuckmere Haven (also known as the Cuckmere Estuary) is an area of flood plains in Sussex, England where the river Cuckmere meets the English Channel between Eastbourne and Seaford. The river is an example of a meandering river, and contains several oxbow lakes. It is a popular tourist destination with an estimated 350,000 visitors per year, where they can engage in long walks, or water activities on the river. The beach at Cuckmere Haven is next to the famous chalk cliffs, the Seven Sisters.
At low tide, one can spot ironwork in the sea close to the river mouth. This is the wreck of the Polynesia, a German sailing ship that ran aground in April 1890 west of Beachy Head; it was laden with a cargo of sodium nitrate.
The beach was commonly used by smugglers in the 16th, 17th, and 18th centuries. For example, in 1783 two gangs of smugglers (each numbering 200 or 300) overcame officers of the law by weight of numbers and carried away a large quantity of goods.
In the Second World War, the site was studied by the Luftwaffe as they flew missions to identify potential landing sites for the invasion of the UK mainland. As a result, the British constructed a series of counter-landing defences, of which numerous pillboxes, anti-tank obstacles, ditches and tank traps survive.Admiralty scaffolding blocked the inlet, but is now gone. Cuckmere Haven featured heavily in the war effort: at night lights were placed to confuse bombers into thinking they were above Newhaven and an airfield was set up further inland. In addition to the permanent land-based constructions, the river was heavily mined.