Nazi Megastructures - Season 3 Episode 2 -

By early 1943 Nazi Germany is losing the battle in the Atlantic. Their U-Boat menace is no longer invulnerable to attack; it could cost them the war. But Hitler and Kriegsmarine High Command are one step ahead. Since 1940, they’ve been planning a submarine capable of fast underwater speeds and phenomenal firepower that will outperform anything that has gone before. Designated the Type 21, it’s the world’s most advanced submarine: Hitler’s sea-faring super weapon.