Renowned for partaking in the first gravity measurements at sea, the USS S-21 (SS-126) was built at Bethlehem Shipbuilding Corporation in 1918. The submarine was also used in the first gravimetric observations at sea conducted by the United States. While it is not a certainty, asbestos might have been present in the wall insulation of the vessel, which means a considerable health danger to those who were present on it. The submarine was decommissioned in 1942, then transferred to the Royal Navy to finally be sunk as a target in 1945. All ships in the Navy commissioned before the 1980s contained enormous amounts of asbestos products. As asbestos breaks down, it can exist in filaments that are hundreds of times thinner than the size of human hair and can be easily dispersed through handling or wind. These filaments can be inhaled or swallowed, and remain dormant in the body for up to 50 years. The damage caused by inhaling asbestos fibers can often be hidden for decades, and many veterans have been blindsided by the development of asbestosis or mesothelioma.