The crew finishes resupplying and departs for Italy. As they carefully approach the Strait of Gibraltar and are just about to dive, they are suddenly attacked and heavily damaged by a British fighter plane, wounding the navigator, Kriechbaum. The captain orders the boat directly south towards the North African coast at full speed determined to save his crew even if he loses the boat. British warships begin shelling and they are forced to dive. When attempting to level off, the boat does not respond and continues to sink until, just before being crushed by the pressure, it lands on a sea shelf, at the depth of 280 metres. The crew works desperately to make numerous repairs before running out of oxygen. After over 16 hours, they are able to surface by blowing their ballast tanks, and limp back towards La Rochelle under cover of darkness.