If the movie takes place aboard a submarine, certain archetypal scenes must occur.
Red light bathes the inside of the sub as the captain whispers orders to the crew.
The men hold their breath and look worried as depth charges explode nearby, shaking the ship and seemingly causing every other valve to spring a leak. The damaged sub sinks to a depth beyond the limit of its gauges, and the hull groans as the water pressure threatens to crush it like a tin can. The plot will pivot on such turnabouts. But Berlin must never know. The codes would be changed, making the exercise meaningless.