The SMS U-517 was a German Navy submersible during the Second Great War. In late 1943 the U-517 secretly rendezvoused with the U.S. Navy destroyer escort Josephus Daniels in the Atlantic Ocean. The captain passed a package to the captain of the Josephus Daniels. Unbeknownst to anyone present, the contents were technical papers to assist the U.S. in developing the superbomb.