It was a forlorn, silly shot. They were end on to him, and the torpedo just ran between two of them and smashed up against the steep shore behind. The track of it on the sea was wide and white as a high road, and half a dozen destroyers were on to that submarine even before the shot had exploded against the rocks. Fritz got down safely—he was clever, but too darned nervous for under-water work—and then began a hunt which was exactly like one has seen in a barn when terriers are after rats. The destroyers and motor patrols were everywhere, and above them flew the seaplanes with observers who could peer down through a hundred feet of water. In a shallow harbour Fritz could have sunk to the bottom and lain there till after dark, but we have 200 fathoms here with a very steep shore and there was no bottom for him. A submarine can’t stand the water pressure of more than 200 feet at the outside. He didn’t dare to fill his tanks and sink, and could only keep down in diving trim so long as he kept moving with his electric motors and held himself submerged with his horizontal planes. Had the motors stopped, the submarine would have come up, for in diving trim it was slightly lighter than the water displaced. All we had to do was to keep on hunting till his electric batteries had run down, and then he would be obliged to come up. Do you twig, Pongo?” “But he could have sunk to the bottom if he had chosen?” “Oh, yes. But then he could never have risen again. To have filled his tanks would have meant almost instant death. At 200 fathoms his plates would have crumpled like paper.” “Still I think that I should have done it.”