Did the crew feel the pressure?

Not just from the compression of the hull. The pressure hull kept the atmosphere inside the boat close to what it was at sea level. It was similar to, but the opposite of what you feel in an airplane. The atmosphere in an airplane is less than sea level but you don’t generally notice. The important thing was that sailors did not need to decompress when the boat came up from the depths.

There were times when air was added to the boat and that could be noticeable. For example, if many torpedoes were fired, the air and water needed added pressure to the air in boat. However, it still wasn’t enough to cause the sailors to need to decompress.