Episode 2 shows the development of the submarine in the Second World War until today. They were celebrated as a "miracle weapon" by Nazi propaganda. The myth of invincibility clung to them. The reality in the Second World War was different: Two thirds of the submariners lost their lives during the missions.

Episode 1 documents the beginnings of submarine development at the end of the 19th century until the outbreak of the Second World War. The two-part documentary takes a multi-faceted journey through history. Submariners, historians and military experts put the events into context.