Saturn Is Less Dense Than Water

Saturn’s average density is about 0.69 grams per cubic centimeter, less than that of water.

The planet is mostly hydrogen and helium. That has led to the popular image of Saturn floating in a big enough bathtub, though you would need a truly enormous tub and it would not end well for the planet.

Check it yourself

NASA’s Planetary Fact Sheet lists mean density for every planet. Water is 1.0 on that scale.