Cotton is a solid which has minute (porous) holes. The pores tend to trap the air and thus the density of cotton becomes less than that of the water. The cotton becomes lighter than water and floats on water.

Does a ball float?

Although the bubble wrap makes the ball weigh a little more, it also displaces extra water making the ball more buoyant. The pockets of air in the bubble wrap mean that the ball and bubble wrap together are less dense than the water, which means the ball floats!

What is the characteristic of a cotton balls?

Cotton balls are made from pure cotton fibre. They are incredibly light because most of their volume is just empty space filled with air. Cotton is a natural plant fibre made of cellulose. Each single fibre is a tiny hollow tube, like a microscopic straw, coated in a thin layer of wax.