"It's a game. Some of the sporting fishermen in the flotilla say that it's much like fishing ... now you use this bait, now that, now this rod, now another, and all the time you are following ... following the fish.... It's a game, the biggest game in all the world, for it has the biggest stakes in all the world. There's far more strategy to it than one would suspect. You see, it's not enough to hang round till a periscope pops up; we've got to fish out the periscope." "Fishing, then," said I. "Well, how and where do you fish?" "On the chequer board of the Irish Sea and the Channel. You see the surface of the endangered waters is divided up into a number of squares or areas, and over each area some kind of a patrol boat stands guard. She may be a destroyer, ... perhaps a 'sloop.' Now let's suppose she's out there looking for 'fish.'" "Yes, even as a fisherman might wade out into a river in which he knows that fish are to be caught. But how is your destroyer fisherman to know just what fish are to be caught, and in just what bays and inlets he ought to troll?" "That's the function of the Naval Intelligence. Have you realized the immense organization which Britain has created especially to fight the submarine? You'll find it all in the war cabinet report for 1917. Before the war, there were only twenty vessels employed as mine sweepers and on auxiliary patrol duties; to-day the number of such craft is about 3,800, and is constantly increasing. And don't forget the sea planes, balloons, and all the other parts of the outfit. So while our destroyer fisherman is casting about in square x, let us say, all these scouting friends of his are trying to find the 'fish' for him. So every once in a while he gets a message via wireless, 'fish seen off bay blank,' 'fish reported in latitude A and longitude B.' ... If these messages refer to spots in his neighbourhood, you can be sure that he keeps an extra sharp lookout. So no matter where the fish goes, there is certain to be a fisher." _During a recent month the mileage steamed by the auxiliary patrol forces in British home waters exceeded six million miles_. "Now while you are beating the waters for them, what about the fish himself?"