The planet Saturn
A planet's weight does not determine whether it can float in water. It's density is what determines that. Your question should be "Which planet's density is so small that it could float in water?"
SATURN.
So light it would actually float on water.
Saturn is the planet that is so light that it could float on water. Its average density is less than water, which gives it the unique characteristic of being able to float in a large enough body of water.
Saturn
The planet Saturn could theoretically float on giant planet like Jupiter because Saturn has a lower density than Jupiter due to its composition being mostly gas and liquid. This would mean that Saturn would have the ability to "float" in the atmosphere of Jupiter, similar to how a boat floats on water.
Saturn is a gas planet, and if it were possible to place it in water it would float. Not sure if the rings would float, but, the planet itself would.
There is no known planet that would be able to float in water, as planets are much larger and denser than water. However, hypothetical lightweight planets made of less dense materials like ice or certain gases could potentially float in a giant body of water if it existed on a massive scale.
Saturn would float in water if you could find a big enough tub and the water to fill it.
Saturn has a very low density and it would be able to float on water. The density of Saturn is: 0.687 grams per cubic centimeter.
Saturn could float in water, because it has a density of 0.7 that of water. That is, however, a theoretical construct, because you would need an enormous pool of water, with a gravitational field much larger than anything we have, in order to achieve that state.
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