THE ENEMY BELOW (WW2 movie 1957)

It is some time in the middle of World War II. The American Buckley-class destroyer escort USS Haynes is on patrol in the South Atlantic. Lieutenant Commander Murrell, a former Third Mate in the Merchant Marine and now an active-duty officer in the Naval Reserve, has recently taken command of the ship; he joined the Navy after his freighter was sunk by a German U-boat, and is still recovering from injuries incurred in the sinking of his previous Navy warship and 21 days marooned adrift afterwards.

Before the U-boat is first spotted, one sailor questions the new captain's fitness and ability. Once a skilled game of cat-and-mouse tracking the U-boat gives way to a series of even more finely honed and intuitive attacks, the crew falls in strongly behind their new skipper.

Murrell is matching deadly wits with U-boat Kapitän zur See von Stolberg, a wily former World War I Unterseeboot skipper deep into a conflict he resents for a Nazi regime he detests. As the battle that emerges tests both commanders and their crews, each man grows to respect his opponent as he discovers his rival can read his mind.