Then again I faintly remember reading that they started being escorted by flak barges, or was that the Bay of Biscay? I need to find that book again...
But you can see the problem imposed especially as allied air power increased...one little covert radio transmission and two hours latter bomb or rocket laden attack aircraft fly straight up the canal and catch a u-boat unalbe to dive or even manuever very well....
But also I believe this was more of a precieved threat. I've never heard of any u-boats sunk in the canal. Has anyone? :hmm: