Note 24 — III THE LANDING
Reading edition
A submarine cannot attack until it has risen near enough to the surface to lift its periscope above water. Having thus obtained its aim, it submerges again only deep enough to conceal the periscope. It fires its torpedo blind when submerged. If it dives too deep, it might send the weapon harmlessly under the ship’s keel. Hence, it is possible, often, to “spot” the disturbed, whitened water above a submarine even though it is sunken out of sight.