Brian, Stewie, and Mort travel back in time to the Nazi regime in Germany. They steal a German U-boat to escape to the safety of England. This clip depicts U-boats and their primary weapon during the war, the torpedo.
A U-boat crew hears the alarm sound and prepares for an emergency dive. After the crew is in position, the captain reveals that it was only a practice drill so they don't get rusty in the event of a real emergency. Such drills help the crew escape the U-boat in the event of a mechanical failure or an attack by an enemy.