A Cartesian diver is a classic experiment, named for René Descartes, which demonstrates the principle of Buoyancy.

The "bottle angel" or the cartesian diver is a toy with the physical background. There are thus different pressure gradients in a fluid demonstrated. You need a bottle - preferably a plastic bottle - the brim is filled with water.

Pressing this bottle you can dance to the angel. The toy is ca. 5 cm high.

You buy a product brand Lauscha art glass.