Perhaps the most bizarre choice of material humans ever made to make a vessel that floats was reinforced concrete. For centuries ships have been made of wood, which later gave way to tougher materials such as steel. But steel was expensive and not readily available, which became a major issue during the World Wars when there was an acute shortage of the metal.

Long before the war, in 1848, Joseph-Louis Lambot, the inventor of reinforced concrete, tried and successfully fashioned a small boat out of ferrocement, jumpstarting the small and short-lived industry of concrete shipbuilding. Before long, ferrocement barges were regularly plying the canals of Europe, and just as the century was drawing to an end, an Italian engineer made the first concrete ship.

The concrete ship SS Palo Alto on Seacliff State Beach, California. Photo credit: David Wan/Flickr

As suspected, concrete was not the most ideal material to build ships with. The basic problem with concrete ships is that they require a very thick hull to be as strong as a steel ship. This made the ship very heavy and consequently burned more fuel to move around. And if the hull is breached, they sink quickly owing to their weight. The sailors of WWI often called them “floating tombstones” and hesitated to serve on them.

Nevertheless, ferrocement ships continued to be made and their sizes gradually increased. The largest of these was the 425-foot SS Selma, an oil tanker launched in 1919. Today, its wreckage remain partially submerged in Galveston Bay in Texas Gulf Coast and visible from both the Houston Ship Channel and Seawolf Park.

After the United States entered the First World War, President Woodrow Wilson approved the construction of 24 concrete vessels as support ships to the Navy. However, none of them could be completed on time and put into service. By the time the ships were ready — only 12 of them— the war had ended. The completed ships were sold to private companies who used them for light-trading, storage and scrap.

Photo credit: Joost J. Bakker/Wikimedia

Similar scarcity of steel occurred during the Second World War, and another 24 concrete ships as well as barges for transporting supplies were commissioned. This time, all ships were completed on time and due to innovations in cement mixing and materials, the second fleet was much stronger than the previous. The ships played an important role during the war, particularly in the D-Day Normandy landings, where they were used for fuel and munitions transportation, and as floating pontoons. Some were fitted with engines and used as mobile canteens and troop carriers.

When war ended, steel was once again available and the more efficient steel ships were back in production. The concrete ships were de-commissioned and towed to various harbors to be sunk or made into breakwater. The largest collection is found at Powell River, British Columbia, where ten of them were arranged in an arc to function as a breakwater. Another nine were sunk in shallow water in Chesapeake Bay off the coast of Kiptopeke Beach, Virginia to create a breakwater for the local ferries.

The oil tanker SS Palo Alto was towed to Seacliff State Beach in Aptos, California, and made into an amusement park with amenities including a dance floor, a swimming pool and a café. The park closed two years later when the company went bankrupt. Today, it’s yet another wreck on the beach, its hull fractured through the mid-section.

SS Palo Alto on Seacliff State Beach, California. Photo credit: Ted Silveira/Flickr

SS Palo Alto on Seacliff State Beach, California. Photo credit: Verifex/Flickr

SS Palo Alto on Seacliff State Beach, California. Photo credit: Don DeBold/Flickr

SS Selma at Seawolf Park in Galveston. Photo credit: Louis Vest/Flickr

The wreck of the San Pasqual, off the coast of Santa Maria, Cuba. Photo credit: phamhoanghai/Panoramio

The Kiptopeke Breakwater in Chesapeake Bay, Virginia. Photo credit: Douglas MacGregor/Panoramio

Breakwater created out of concrete ships at Powell River, British Columbia. Photo credit: David Stanley/Flickr

The wreck of SS Selma at Seawolf Park in Galveston. Photo credit: Katie Mague/Flickr

The wreck of USS Selma at Galveston Bay on the Texas Gulf Coast. Photo credit: Galveston.com/Flickr

Sources: www.concreteships.org / Wikipedia / www.mobileranger.com