On the beach and in the ocean scenes, it switches from night to day. When the driver of the car parked on the beach gets out and shuts the door, there are shadows of him on the car and ground. This happens after he signals to the sub with his headlights, in the dark. When Ralph flies into the side of the submarine, it appears to be day. Lastly, when Bill asks the men on the beach to freeze, it is night again.