As Salvage Sailor posted above the story of Naval Officer Edouard Isaacs is truly remarkable.-his autobio is "Prisoner of the U-90" and first editions of this short book are available on-line. A better reading book is "Escape from Villingen" by D. Messimer. Once picked up by the Uboat that sunk his ship, he was treated with all the respect the Germans felt a fellow officer deserved, including keeping his revolver, and eating at the subs officers Mess. Oddly he was put in the pilots POW camp. He was nearly killed from beatings administered after his escape attempts.
It should be a movie !