Saturn would float if you placed it in a giant bathtub filled with water.

Saturn is a gas giant formed about 4.5 billion years ago. It consists of 96% hydrogen and 3% helium. These are the two lightest elements in the universe. Because of this, Saturn has a density of 0.687 grams per cubic centimeter. Water has a density of 1 gram per cubic centimeter.The planet does have a heavy rocky core. This core is about 9 to 22 times the mass of Earth. However, the core is surrounded by a massive layer of liquid metallic hydrogen. Above that is a thick layer of gas. These outer layers take up most of the planet's volume but do not weigh very much.To make Saturn float, you would need a body of water over 75,000 miles wide. Other planets in our solar system are much heavier for their size. Earth is the densest planet at 5.51 grams per cubic centimeter. Even other gas giants like Jupiter and Neptune would sink in water.Scientists confirmed these numbers using the Cassini-Huygens spacecraft. This mission orbited Saturn from 2004 to 2017. It measured the planet's gravity and size with high precision. These measurements proved that Saturn is the only planet in our solar system less dense than water.