Saturn would float in a bathtub, if the tub were big enough.
Saturn weighs 95 Earths but is so puffed up that its mean density is just 0.687 grams per cubic centimetre, about 30 percent less than water. It is the only planet in the Solar System lighter than water. The gas giant is mostly hydrogen and helium and has 293 known moons.
Useful: Density, not mass, decides floating: a steel ship floats, a steel ball doesn't.
Source: en.wikipedia.org