Excellent story of exploration and discovery in France during WWII and the attendant hardships of getting to the caves, keeping explorers interested when all out war was raging around them, and developing equipment with limited means in an effort to set a world depth record in the caves of France. Even thought the bulk of this story happens during the German occupation of France, that seems to be only a tangential aspect of the story in that it was a minor irritation to the continuation of exploration of the cave system. My hat is off to these early explorers and to the drive and determination they showed in their desire to explore and document.