Saturn Is Less Dense Than Water

Saturn’s average density is 687 kg/m³, about 0.69 times the density of water, which is 1,000 kg/m³. A bathtub big enough to hold the planet would float it.

Saturn is about 95 times as massive as Earth, but its volume is roughly 760 times larger. The mass is spread thin because the planet is mostly hydrogen and helium, the two lightest elements, with only a small rocky core. Saturn also spins fast enough to flatten it into an oval, and its low density keeps it puffy. Among the planets, only Saturn has an average density below that of water.