How do submarines dive and surface?
To dive or submerge the submarine, valves on the top of the very large ballast tanks are opened. This allows the air in the tanks to escape; at the bottom of the tanks are holes that allow the seawater to flood in. As water is heavier than air, the submarine becomes heavier and therefore sinks in a controlled manner. To surface the submarine, the valves on the top of the ballast tanks are shut, high-pressure air is pumped into the tanks and the water is forced out through the holes at the bottom. The tanks fill with air and “float” the submarine to the surface.
