Concrete ships are built of steel and ferrocement (reinforced concrete) instead of more traditional materials, such as steel or wood. The advantage of ferrocement construction is that materials are cheap and readily available, while the disadvantages are that construction labor costs are high, as are operating costs. (Ferrocement ships require thick hulls, which results in either a larger cross-sectional area that hurts hydrodynamics, or leaves less space for cargo.) During the late 19th century, there were concrete river barges in Europe, and during both World War I and World War II, steel shortages led the US military to order the construction of small fleets of ocean-going concrete ships, the largest of which was the SS Selma. United States Maritime Administration (MARAD) designation for concrete ships-barges was Type B ship. Few concrete ships were completed in time to see wartime service during World War I, but during 1944 and 1945, concrete ships and barges were used to support U.S. and British invasions in Europe and the Pacific. Since the late 1930s, there have also been ferrocement pleasure boats. History The oldest known ferrocement watercraft was a dinghy built by Joseph-Louis Lambot in Southern France in 1848. Lambot's boat was featured in the Exposition Universelle held in Paris in 1855. Beginning in the 1860s, ferrocement barges were built in Europe for use on canals, and around 1896, an Italian engineer, Carlo Gabellini, began building small ships out of ferrocement. The most famous of his ships was the Liguria. Between 1908 and 1914, larger ferrocement barges began to be made in Germany, United Kingdom, the Netherlands, Norway and United States. The remains of a British ship of this type, the auxiliary coaster Violette (built 1919), can be seen at Hoo, Kent, England. On August 2, 1917, Nicolay Fougner of Norway launched the first self-propelled ferrocement ship intended for ocean travel. This was an vessel of 400 tons named Namsenfjord. With the success of this ship, additional ferrocement vessels were ordered, and in October 1917, the U.S. government invited Fougner to head a study into the feasibility of building ferrocement ships in the United States. The Fougner Concrete Shipbuilding Company, Flushing Bay, New York, reported calculated cost was of $290 per deadweight ton for the Cape Fear (List of shipwrecks in 1920 "10.21 30 October") and the Sapona which they presumably built. About the same time, the California businessman W. Leslie Comyn took the