How Do Submarines Work?
Submarines are incredible machines that can travel underwater for months! But how do they dive and come back up?
The secret is BALLAST TANKS — special compartments that can be filled with water or air. When the sub needs to dive, valves open and seawater floods into the ballast tanks. The sub gets heavier and sinks. When it needs to rise, compressed air is pumped into the tanks, pushing the water out. The sub gets lighter and floats up!
It is the same idea as when you fill a water bottle — it sinks. When you empty it and fill it with air, it floats!
Modern nuclear submarines can stay underwater for 3 months without surfacing! They make their own oxygen from seawater and their own fresh water. The only reason they surface is to get more food for the crew.