Mulberry Harbours were unfoldable harbours developed during the Second World War in order for the allies to constitute a basis able to make all the cargo land in Arromanches (Normandy). Apart from the bridges and piers, what is very interesting here is the constitution of a seawall in order to break the waves that could have -and that actually had- avoid the harbour to function. This seawall was composed by ships in the surface and enormous concrete caissons (called Phoenix) that was filled with water or sand and sank in order to break the deeper currents.
If you are interested to know more I recommend this US Navy’s history’s website.
This article seemed relevant within the frame of Transit-City’s next workshop in Paris on February 19th which will discuss about the military understanding of urban issues and design.