"The fish himself? Well, the ocean is a pretty big place, and the fish has the tremendous advantage of being invisible. A submarine need only show _three inches_ of periscope if the weather is calm. She can travel a hundred miles completely submerged, and she can remain on the bottom for a full forty-eight hours. Squatting on the bottom is called "lying doggo." But she has to come up to breathe and recharge her batteries, and this she does at night. Hence the keenness of the night patrol. And here is another parallel to fishing. You know that when the wind is from a certain direction, you will find the fish in a certain pool, whilst if the wind blows from another quarter, you will find the fish in another place? Same way with submarines. Let the wind blow from a certain direction, and they will run up and down the surface off a certain lee shore. You can just bet that that strip of shore is well patrolled. Moreover, submarines can't go fooling round all over the sea, they _have_ to concentrate in certain squares, say the areas which lie outside big ports or through which a great marine highway lies." "Suppose that you manage to injure a fish, what then?" "Well, if the fish isn't too badly injured, he will probably make for one of the shallows, and lie doggo till he has time to effect repairs. Result, every shallow is watched as carefully as a miser watches his gold. And sea planes have a special patrol of the coast to keep them off the shallows by the shore." "Sometimes, then, in the murk of night, a destroyer must bump into one by sheer good luck?" "Oh, yes, indeed. Not long ago, a British destroyer racing through a pitch dark rainy night cut a sub almost in half. There was a tremendous bump that knocked the people on the bridge over backward, a lot of yelling, and then a wild salvo of rain blotted everything out. I think they managed to rescue one of the Germans. Pity they didn't get the fish itself. You know it's a great stunt to get your enemy's codes. We get them once in a while. Ever seen a pink booklet on any of your destroyer trips? It's a translation of a German book of instructions to submarine commanders. On British boats they call it 'Baby-Killing at a Glance or the Hun's Vade Mecum.' Great name, isn't it? Tells how to attack convoys and all that sort of thing. Lots of interesting tricks like squatting in the path of the sun so that the lookout, blinded by the glare, shan't see you; playing dead and so on. That playing-dead stunt, if it ever did work, which I greatly doubt, is certainly no favourite now." "Playing dead? Just what do you mean?"