In 1944, Atze Schröder pretends to be the legendary Lieutenant Commander Roenberg when the Germans send their last available submarine, the U-900, on a secret mission from Toulon to Warnemuende.

It is the year 1944 and World War II is not over yet. The Germans want to send their last available submarine, the U-900, on a secret mission from Toulon to Warnemuende. Atze pretends to be the legendary Lieutenant Commander Roenberg. But the crew gets suspicious when their commander starts issuing unconventional orders.—American Film Market

With a business idea of historic significance, Atze Schröder (one of Germany's most successful comedians), Oliver K. Wnuk and Yvonne Catterfeld embark on an adventurous voyage. Thanks to Atze's presence on board, one impossible situation follows the next - disaster guaranteed. But with their keen sense for risky escape routes, the three protagonists of this adventure comedy display irresistible charm and astonishing seaworthiness.—Wiedemann & Berg Film