How Do Submarines Dive Deep and Come Back Up Without Sinking?

Submarines are amazing underwater ships that can dive thousands of feet below the ocean surface and then pop back up again. But how do they control whether they sink or float? The secret is all about controlling their weight using special tanks.

Every submarine has big tanks called ballast tanks built into its sides. When the submarine wants to dive, it opens valves that let ocean water rush into these tanks. The extra water makes the submarine heavier than the water around it, so it sinks down into the deep blue sea.

When it is time to come back up, the submarine uses compressed air to push the water back out of the ballast tanks. As the water leaves, the submarine becomes lighter than the water around it. Just like a beach ball pops up to the surface of a pool, the submarine rises back toward the sunshine above.

Submariners can control exactly how deep they go by letting in just the right amount of water. They can float at any depth they choose, hover like a helicopter underwater, or cruise along without touching the bottom. It is like having an elevator that works in the ocean!

This clever system of filling and emptying tanks lets submarines explore the mysterious ocean depths and return safely home. Scientists, explorers, and sailors use submarines to discover shipwrecks, study sea creatures, and learn secrets hidden beneath the waves.