Enhydros from Madagascar

The majority of quartz crystallises in a hydrothermal environment, the result of rapid cooling of silicon and oxygen in either molten magma flows or within hot thermal vents.
Enhydro quartz is transparent crystalline quartz with water-filled internal cavities. Enclosed in negative voids within the stone, there may be a bubble of air which has evaporated out of the liquid as the growing quartz crystal cooled.
If there is sufficient space enough to allow it, these air bubbles move within the cavity as the stone is rotated.
Liquid filled negative spaces within gems are common, but magnification is usually needed to observe them.
however, in some cases where the stone and the void are large enough, the movement is visible to the naked eye, making such examples highly collectable gem rarities.