Your question is probably based on the often quoted statement that if Saturn were placed in a body of water large enough, it would float. That is based on its average density, calculated by dividing total mass by volume. Archimedes' principle tells us that a body will float in a fluid if its average density is less than the fluid's average density. Since water's density is 1 gm/cm3, and Saturn's average density is 0.7 gm/cm3, a sphere of the same size and mass would float on water. Jupiter's average density is 1.4 gm/cm3, so a sphere of its size and mass would sink.
In fact, both Saturn and Jupiter are gaseous planets. There is no solid surface defining their outer diameters, so trying to float either would not be possible even if a large enough ocean could be found.
Answered by: Paul Walorski, B.A., Part-time Physics/Astronomy Instructor
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