This is the part of the submarine that holds the submarine's crew, machinery, and anything else that must be kept inside. The pressure hull keeps everything inside the submarine from being crushed from the high pressure of the water at deep depths.
Ballast Tanks
These are built into each end of the submarine. These allow the submarine to dive; when they are filled with sea water, the submarine goes down into the water.
Diving Planes
These are movable surfaces on the outside of the submarine that control the submarine's movements under the water.
Rudders
The rudders steer the ship. Crewmen can turn a rudders to the left or right to make the submarine change course.
