Cotton is solid but it floats on water. Why?

Cotton is solid but it floats on water because it has a low density than water, due to its porous structure, which traps air inside itself.

Archimedes’s law states that a body immersed in water displaces its volume of water, and if this displaced volume of water weighs more than the body immersed, the body will float. If it weighs less than the body, the body will sink.

In simple terms, if the density of a solid is less than the density of a liquid, the solid will float on the liquid.