He had passed through the net, he thought, but suddenly observed that he was towing a portion of it with him. The boat began to sink quickly, bows down; the foremost hydroplane jammed. He immediately forced her nose up, by blowing ballast tanks and driving her at full speed. But, even in that position, she continued to sink till she reached 245 feet. At that depth the pressure was tremendous. The conning-tower scuttles burst in, and the conning-tower filled with water. The boat leaked badly, and the fore compartment had to be closed off to prevent the water getting into the battery, where it would have produced the fatal fumes of chlorine gas. For ten mortal minutes the commander wrestled with his boat. At last, by putting three men on to the hydroplane with hand-gear, he forced the planes to work and the boat rose. He just managed to check her at twelve feet and got her down to fifty, but even at that depth six patrol vessels could be heard firing at her--probably she was still towing something which made a wake on the surface. Blind, and almost unmanageable, E. 12 continued to plunge up and down, making very little way beyond Nagara. The conning-tower and its compass were out of action, but the commander conned his boat from the main gyro compass, and when both diving gauges failed he used the gauge by the periscope. The climax was reached when at eighty feet, just to the south of Kilid Bahr, another obstruction was met and carried away. But this was a stroke of luck, for when the commander, by a real inspiration, put on full speed ahead and worked his helm, the new entanglement slid along the side of the boat and carried away with it the old one from Nagara. The boat rose steeply by the bow and broke surface. Shore batteries and patrols opened fire, and a small shell cracked the conning-tower; others hit the bridge, and two torpedoes narrowly missed her astern. But she came safely through to Helles, and reached her base after a cruise of over 2,000 miles.