What makes a submarine able to float and sink?
A submarine changes its buoynacy so it can float on the water surface and cruise below the surface. (The submarine sinks by letting water into its ballast tanks. The submarine floats by pumping that water out.) Submarines have ballast tanks outside of the area where the crew live and work. To sink, some of the air is let out of the tanks and some water is let in. To float back up, more air is forced into the tanks, squeezing some water out. Valves control how that happens and how much water/air. Extra air is compressed and kept in bottles. Once the air/water mix is just right in the ballast tanks the sub has “neutral bouyancy” — that means it won’t sink further or float higher. The sub is then driven pretty much like an airplane, controlled by small wings fore and aft. Submarines have ballast tanks inside that they can flood with water which makes the boat sink. They also have compressed air tanks on board from which they use the compressed air to force out the water from the ballast
