The USS S-16 (SS-121) was an S-boat, commissioned in 1920. She was the largest submarine the U.S. Navy operated in that period. The new vessel was was designed submerge to depths as deep as 200 fsw.  The S-16 served in the Pacific fleet until 1935 but was recommissioned in 1940 as World War II loomed. She patrolled the Caribbean until considered obsolete in 1944.  In 1945 the S-16 was finally sunk as a target off of Key West, FL. in 1945. She now rests upright in 255 fsw, a depth deeper than her original maximum dive depth.