This is a neat little trick, an aluminum foil boat is floated on Sulfur Hexaflouride Gas in a tank.
Hexaflouride is an interesting compound, here are its specs… Colorless Odorless Non-toxic Non-flammable gas Typical for a nonpolar gas, it is poorly soluble in water but soluble in nonpolar organic solvents.
It is generally transported as a liquified compressed gas. It has a density of 6.13 g/L at sea level conditions. It is used primarily in the electrical industry as a dielectric for High Voltages 'Because the gas has a high density (over five times denser than air), it can be poured into open containers, like beakers and fishtanks.
Moreover, light objects, e.g. ship-like vessels made out of light wood or aluminium foil containing air inside, can float on the gas.' An impressive video that would be fun to reproduce, if that is, you could ever get your hands on any Sulfur Hexaflouride, something tells me your local chemist won't stock it