On a lighter note, the War Departments asked people for ideas on how to defeat the U-Boats. Will Rogers offered "Drain the Atlantic". When asked how he would do that, he said he just comes up with ideas and leaves it to others on how to implement them.
Actually, the studies done in the 70s for the resupply of Europe said the most cost effective approach was to buy more targets. Attack submarines were the best defense, but it was still more cost effective to buy more transports. As you can imagine, this report was not widely distributed, and its author never made Admiral.