They all were sunk by running into minefields, and by the way, the snorkel device was not invented by the Germans, but by the Dutch. When Germany invaded Holland in 1940 they captured 5 Dutch submarines equipped with the device. It was improved and later fitted to U Boats when they were being sunk Willy Nilly. Just another fact, the Germans didn't invent Enigma either, that was a Swedish idea, Germany bought some machines in 1938 from the Swedes, as did Poland, and rumour has it, UK as well.