Over 200 canisters had detonated above and around us by 01.00. Several times we had used a ruse in an effort to escape. Through an outboard valve, we repeatedly expelled a great mass of air bubbles. These screens of air oated away on the current, reecting the Asdic impulses like a large solid body. But our attackers were fooled into chasing the decoys only twice, and both times they left at least one vessel behind, directly over our heads. Unable to sneak away, we gave up the game and concentrated on conserving our power, our compressed air, and our dwindling supply of oxygen.