The Diver

We often dive into things because we are curious. In order to dive into the sea, you must be able to control the gas inside the body and breathe under water.

At the top of the container is a small diver attached to a balloon. If you press the handle at the bottom of the water-filled container, you increase the pressure inside and the diver will go down. When you release the handle, the pressure falls and the diver goes back up towards the surface.

Bony fish do the same thing to position themselves in the water by emptying or filling their swim bladder to move up and down. The gas in the fish’s swim bladder can be compressed just like the liquid in the diver experiment.

Cartilaginous fishes, such as sharks and rays, do not have a swim bladder. For this reason, they have to always keep moving in order not to sink to the bottom.