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?"
No, the density of Uranus is 1.27 g/cm3 (the density of water is 1.00 g/cm3), therefore Uranus would sink. The planet that would float in water is the planet Saturn which has a density of 0.687 g/cm3.
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
Saturn is the planet with a lower density than water, causing it to float if there were a large enough body of water for it to be placed in. Its average density is less than that of water due to its composition of mostly hydrogen and helium gases.
Saturn would float in water if you could find a big enough tub and the water to fill it.
Saturn is less dense than water. So the Answer is 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.
coal can float on water, because water's density is 1.0 g/cm3. and nothing is able to float on water unless it's density is less than water's density (; hope this helps you out! coal can float on water, because water's density is 1.0 g/cm3. and nothing is able to float on water unless it's density is less than water's density.
Saturn is the least dense planet, only 0.7 g/cc on average (less than water's density). If you could put Saturn in bathwater, it would float.
It's actually pretty easy. If the density of the substance is higher than the density of water, the object will sink. If the density of the substance is lower than the density of water, the object will float. Be aware though that various substances may have dissolved into the water, thus changing its density. For example, seawater has a different density than fresh water.
Theoretically, the planet Saturn would float when placed in water because it has an average density that is less than the density of water. On the other hand, there is probably not enough water in the solar system to permit the experiment to be performed. If you choose not to consider the planet as a whole, the atmosphere would float on the water but the rocky core would sink like a stone.