Comments by "Sar Jim" (@sarjim4381) on "1942 USCGC Icarus versus U-352 in torpedo alley, Updated episode" video.

They Type VIIC had an "operating depth" of of 220 meters, or 722 feet. That was the German designation of the depth a sub could sink to as long as it was going to sit on the ocean floor and not move in an attempt to escape detection. It was not considered a safe depth normally operate at since any prolonged time at that depth would start popping rivets and generally scare the crap out of the crew. General orders were for Type VIIC to not go deeper than 400 feet unless it was their only option to escape a depth charge attack. There were, however, several of these type that ended up at 900-950 feet, either because the boat was out of control or commanders decided it was worth the risk to escape certain destruction from depth charging. Of those that managed to make it back to France or Norway, the boats had to be totally rebuilt due to the seams and rivets being wracked and bent.
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