The Phoenix breakwater

Breakwater (structure)

Breakwaters are structures constructed on coasts as part of coastal defence or to protect an anchorage from the effects of weather and longshore drift.-Purposes of breakwaters:...

s were a set of reinforced concrete caisson

Caisson (engineering)

In geotechnical engineering, a caisson is a retaining, watertight structure used, for example, to work on the foundations of a bridge pier, for the construction of a concrete dam, or for the repair of ships. These are constructed such that the water can be pumped out, keeping the working...

s built as part of the artificial Mulberry harbour

Mulberry harbour

A Mulberry harbour was a British type of temporary harbour developed in World War II to offload cargo on the beaches during the Allied invasion of Normandy....

s 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

Selsey

Selsey is a seaside town and civil parish, about seven miles south of Chichester, in the Chichester District of West Sussex, England. Selsey lies at the southernmost point of the Manhood Peninsula, almost cut off from mainland Sussex by the sea...

, and then towed across the English Channel

English Channel

The English Channel , often referred to simply as the Channel, is an arm of the Atlantic Ocean that separates southern England from northern France, and joins the North Sea to the Atlantic. It is about long and varies in width from at its widest to in the Strait of Dover...

 and sunk to form the Mulberry harbour breakwaters replacing the initial 'Gooseberry' block ships. Further caisson were added in the autumn of 1944 to re-enforce the existing structure to cope with the harbour continuing in use longer than planned.

Several Phoenix breakwaters are still in use in Britain: two are part of the harbour off Castletown at Portland Harbour

Portland Harbour

Portland Harbour is located beside the Isle of Portland, off Dorset, on the south coast of England. It is one of the largest man-made harbours in the world. Grid reference: .-History:...

 and two can be dived in less than 10 metres of water off Pagham

Pagham

Pagham is a coastal village and civil parish in the Arun district of West Sussex, England, with a population of around 5,500.-Geography:The village comprises three main areas:*Pagham Beach, coastal area, developed in the early 20th Century,...

. There is also a smaller Phoenix Caisson (type C) in Langstone Harbour

Langstone Harbour

Langstone Harbour is an inlet of the English Channel in Hampshire, sandwiched between Portsea Island to the south and west, Hayling Island to the south and east, and Langstone to the north. Geographically it is a ria....

.

Four Phoenix breakwaters were used in the Netherlands

Netherlands

The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

 to plug a gap in the dyke at Ouwerkerk after the North Sea Flood of 1953

North Sea flood of 1953

The 1953 North Sea flood was a major flood caused by a heavy storm, that occurred on the night of Saturday 31 January 1953 and morning of 1 February 1953. The floods struck the Netherlands, Belgium, England and Scotland.A combination of a high spring tide and a severe European windstorm caused a...

. They have now been converted into a museum for the floods called the Watersnoodmuseum. You can walk through the four caissons.