The fishermen would sometimes have rescued their ruthless enemies if they could have disentangled them in time. But this could rarely be done; and the Germans met a just fate. One day a submarine came up alongside a British trawler which was engaged in its regular fishing, was quite unarmed, and had a crew of old men and young boys. The Germans took all the fresh fish they wanted, sank the trawler, smashed up her boats, and put the fishermen on the submarine's deck. Then they slammed-to the hatch of the conning tower and sank very slowly, washing the fishermen off. Then they rose again to laugh at them drowning. An avenging destroyer came racing along and picked up the sole survivor. But the German jokers, seeing it coming, had gone. No wonder the seafaring British sometimes "saw red" to such a degree that they would do anything to get in a blow! And sometimes they did get it in, when the Germans least thought it was coming. When a skipper suddenly found a German U-boat (_Unterseeboot_ or under-sea-boat) rising beside him, just as his engine-room mechanic had come up with a hammer in his hand, he called out, "look sharp and blind her!" Without a moment's hesitation the mechanic jumped on her deck and smashed her periscope to pieces, thus leaving her the blinded prey of gathering destroyers. The Germans put their wits to work with hellish cunning. They wanted to surround Great Britain with a sea of death so full of mines and submarines that no ship could live. The mines were not placed at random, but where they would either kill their victims best or make them try another way where the lurking submarines could kill them. The sea-roads into great ports like London and Liverpool converge, just as railway tracks converge toward some great central junction. So submarines lying in wait near these crowded waters had a great advantage in the earlier part of the war, when people still believed that the Germans would not sink unarmed merchantmen on purpose, especially when women and children were known to be on board.