The Phoenix breakwaters were a set of reinforced concrete caissons built as part of the artificial Mulberry harbours that were assembled as part of the follow-up to the Normandy landings during World War II. They were constructed by civil engineering contractors around the coast of Britain. They were collected at Dungeness and Selsey, and then towed across the English Channel and sunk to form the Mulberry harbour breakwaters replacing the initial 'Gooseberry' block ships.