Ship Control Station The lowest ranking of the enlisted men are traditionally assigned the duty of planesman and helmsman. Their controls function much like the controls on an airplane: maneuvering in and out and turning left and right. The immediate superior to the planes and helmsman is the diving officer, who sits behind them. The Chief of the Watch sits outboard and uses the ballast control to adjust the trim of the submarine by adding or removing water from the variable ballast tanks, thereby adjusting the sub's buoyancy. Diagram reprinted from Tom Clancy's Submarine: A Guided Tour Inside a Nuclear Warship, Laura Deninno, Series Illustrator.