Space
Would Saturn float in water?
The short answer
On average, yes. Saturn's mean density is about 0.69 grams per cubic centimetre, lower than water's 1.0, making it the only planet in the solar system less dense than water. Given a big enough bathtub, it would float.
Saturn carries about 95 times the mass of Earth, which sounds decisive until you notice it spreads that mass across a volume more than 750 times larger. The result is a planet made mostly of hydrogen and helium that is, on average, lighter than the stuff in your kettle.
NASA puts it plainly: Saturn is the only planet in our solar system whose average density is less than water. The bathtub version of the fact is a thought experiment rather than a proposal, and it falls apart the moment you take it literally. Any ocean big enough to hold Saturn would be crushed into something that isn't liquid water, and Saturn's own gravity would swallow the tub.
The honest version is still lovely. It isn't that Saturn is small. It's that Saturn is enormous and mostly air.
Source
- Saturn: FactsNASA Science