Somebody mentioned earlier in this thread that DCs did not have the power to shake a u-boat's hull. Well I think this disproves that. A nerve-wracking excerpt from my fave sub book 'Hirschfeld'.
"The inferno broke loose with such devastating violence it seemed that a volcano had erupted around the boat. I wondered how the pressure hull could possibly withstand it. The main lighting slowly failed. The unbelievable din of fifteen great thunderclaps one after the other shook and rolled the submarine, an endless cascade of almost unendurable sound. Then the reverberations growled away and the emergency lighting flickered on." Pgs 38, 39.
A brilliant book with very descriptive accounts. Also I love the sounds that GWX uses for the DCs. Actually I hate them but that's another story.