It's also extremely tense watching the spitfires, because not only do the pilots have to fight the German planes, they have to do it while concentrating on protecting the boats and worrying about a dwindling fuel supply. In the civilian boat, most of the conflict- until the last part of the film- is caused by the presence on board of a shell-shocked soldier whom they have picked up. Even when he causes needless grief, however, it's hard to feel anything but sympathy for him, his nerves shattered by what he has been through.
"We shall go on to the end. We shall fight in France, we shall fight on the seas and oceans, we shall fight with growing confidence and growing strength in the air, we shall defend our island, whatever the cost may be. We shall fight on the beaches, we shall fight on the landing grounds, we shall fight in the fields and in the streets, we shall fight in the hills; we shall never surrender."