Living organisms breathe oxygen into grow

Most living things need oxygen to survive. Oxygen helps organisms grow, reproduce, and turn food into energy. Humans get the oxygen they need by breathing through their nose and mouth into their lungs. Oxygen gives our cells the ability to break down food in order to get the energy we need to survive.

Explanation:

they float because they are less dense than the water itself

something denser than water, like a rock, will sink to the bottom