What is the principle of submarine diving?

In fact, the principle of submarine ups and downs is the same.

The principle of submarine ups and downs is based on Archimedes principle. Archimedes' principle points out that an object immersed in a static fluid is subjected to a buoyancy, the magnitude of which is equal to the weight of the fluid displaced by the object, and the direction is vertical and upward, and passes through the center of mass of the displaced fluid.

All submarines are equipped with ballast tanks. As long as water is injected into the empty ballast tank, the submarine will become heavier. At this time, the weight of the submarine will be greater than the weight of its boiling water (that is, greater than buoyancy), and the submarine will gradually dive. When the submarine floats normally, the water in the ballast tank is squeezed out by high-pressure air step by step, which makes it full of air and reduces the weight of the submarine underwater. When the weight of the submarine is less than the weight of the same volume of water (that is, less than buoyancy), the submarine will float until it comes to the surface.