Andy Anderson - U-Boats
Usually you'd set off to reach a convoy at dawn and you had to be extremely careful because approaching a convoy in the half-light, they were never too sure. So you used to flash the code of the day and never go to near and then you'd show them the silhouette of the airplane and be very careful.
Eventually, when they'd flash back, then you'd say, "Right, now I'll go ahead and escort you." So during the day it was all visual, looking for anything that approached the convoy and at night it was all radar. A U-boat could descend, crash dive in 30 seconds and many, many is the time where our crews would try and reach it, but they'd beat them to it.
So actually, what they did on the squadron was designed a stopwatch with a thing around it and as you looked on the panel on the stopwatch it would determine from the swirl how far ahead you could lay your depth charges, but of course it was all by guess because the U-boat could turn either way. It may not go straight on. And you know, if it was more than, say, a minute then there's no point in doing it because the U-boat would be well below the level of a depth charge which was set at 25 feet.