The S.S. Selma was an experimental oil tanker ship made from concrete during the final months of World War I. The United States experimented with concrete as a shipbuilding material as a way to conserve steel during wartime. Twelve concrete ships were completed by various contractors and proved the viability of the concept. The largest of these were the S.S. Selma, named for the city in Dallas County, and the identical S.S. Latham.

Weighing 7,500 tons, the S.S. Selma's loaded displacement was 13,000 tons. With a length of 434 feet and a beam, or width, of 54 feet at its widest point, it had a draft (distance between the waterline and the bottom of the ship) of 26 feet with a full load of cargo. Its 2,800-horsepower engine drove the vessel at a top speed of 10.5 knots, or about 12 miles per hour. Only the hull of the Selma was concrete. The remainder of the ship was of conventional construction.
The Selma's hull was made up of more than 2,600 cubic yards of expanded shale concrete reinforced by 1,500 tons of smooth steel reinforcing bars. The concrete hull was five inches thick at the bottom, tapering to four inches on the sides of the vessel. When the Selma was originally designed, engineering studies indicated that the concrete had to have a compressive strength (the capacity of a material or structure to withstand loads tending to reduce size) of 5,000 pounds per square inch (psi) and weigh no more than 110 pounds per cubic foot. The expanded shale concrete produced for the construction of the ship easily exceeded this target. Average compressive strength 28 days after pouring was 5,591 psi–more than 10 percent above specifications.
Built by F. F. Ley & Company in Mobile, Mobile County, the S.S. Selma launched on June 28, 1919, the same day World War I officially ended. It was subsequently sold by the government to a private company and entered service as an oil tanker servicing several ports on the Gulf Coast. Its service was cut short when it struck a jetty at Tampico, Mexico, on May 31, 1920, causing a 60-foot crack in its hull.
After temporary repairs were performed, the ship was towed to Galveston, Texas, for full repairs, but the unique construction proved to be a problem because no facilities had the ability to repair concrete hulls. The ship languished in the harbor for almost two years. Ultimately, the owners decided to scrap the ship, and, after removing all useable equipment from the vessel, it was towed to a specially dug channel and sunk off of Pelican Island, Texas, on March 9, 1922. Because the hull is only partially submerged, the ship is still readily visible from points on the shore and from the Bolivar Peninsula Ferry.

More than 90 years after its sinking in the channel, the S.S. Selma is a continuing source of information for concrete and academic experts who study its surprising durability in the face of the many ferocious storms that pound the Texas coast.