I played that mission once as a destroyer. Sometimes people would take advantage of the Messerwetzer feature that allowed you to drive the boat like an airplane. I scored a kill on one of the U-boats when he tried to race from deep water to periscope depth and surprise me. He was the one surprised when he overdid it and surfaced. I immediately locked the director onto him and four 4" guns made short work of him.
On the other hand I once rushed over to investigate a contact - right into the loving arms of a torpedo.
We also had a u-boatman report that he was out of the game. It seems he had put his planes to full rise and forgot to center them once he was coming up. The boat tried to do a loop and when he was vertical everything broke loose and he sank.
One of the features I like the most is the way that the subs can't talk to each other unless they're surfaced, and then the destroyers get an HF/DF warning. Of course TeamSpeak negates that now.