The USS S-18 was a United States Navy submarine, part of the S-class fleet. Launched on March 1, 1923, it was designed for coastal defense and reconnaissance missions. The submarine was 219 feet long and had a surface displacement of 1,000 tons. During its service, the USS S-18 operated primarily in the Pacific and was involved in various training exercises. It was decommissioned in 1931 and later sold for scrap in 1945. The S-class submarines, including the S-18, played a crucial role in the development of submarine technology during the early 20th century.