Following WW1, the US Navy began experimenting with the possibility of submarine observation and scouting aircraft; Submarine S-1 became the experimental platform for this project, late in 1923. She was altered by having a steel capsule mounted aft the conning tower; a cylindrical pod which could house a small collapsible seaplane, the Martin MS-1. After surfacing, this plane could be rolled out, quickly assembled, and launched by ballasting the sub until the deck was awash. The first successful attempt was made on November 5th 1923. However, the program was cancelled after this flight. A total of six Martin MS-1s were built with all six still being carried on US records as late as 1926. Almost nothing is known of their subsequent use.