Having read several first person accounts of operations in the North Atlantic, I'd have to agree that there was some artistic license used, to put it mildly.
Anyway, captains often rammed when they had the chance (which wasn't often), which crushed their bows and rolled the U-boat over onto her beam. If the corvette struck the U-boat fairly then the pressure hull was breached, else the ship only damaged the U-boat's casing, and in some cases where the angle was not acute, the two vessels slid off each other. I believe there was more than one case when that happened of the ship's hull being holed in the machinery spaces by the U-boat's planes.
Regards,
Bruce