During World War I, Lieutenant Winters is discharged from the United States Navy because he stopped to save the survivers of a torpedoed ocean liner rather than pursue the German submarine that bombed the ship. After the war, Winters, now a sea captain, is hired to recover a strong box from the sunken boat. Divers find the box and discover that it contains two wills, one of which bequeaths a fortune to Evelyn Inchcape. A lawyer tries to get the money away from Evelyn, but Winters prevents him from succeeding. One of the divers turns out to be Ludwig, the German submarine captain who sunk the liner, but when Winters hears his story, he drops his plans for revenge. Winters and Evelyn fall in love. More on Wikipedia or Mubi
Watch The Sea Ghost aka U 67 (1931)