Pick one category for the following text. The options are - company, educational institution, artist, athlete, office holder, mean of transportation, building, natural place, village, animal, plant, album, film or written work. German submarine U-821 - German submarine U-821 was a short-lived Type VIIC U-boat of Nazi Germany's Kriegsmarine built by Oderwerke in Stettin during World War II for service in the Battle of the Atlantic. She only participated in two brief combat patrols one of which ended after four days when she was sunk by allied aircraft. U-821 was built in Stettin at a small shipyard and thus took eighteen months to complete being ready by October 1943.
Mean Of Transportation