Does It Sink or Float?

When you put something in water, two things can happen. It can FLOAT — that means it stays on top of the water! A rubber duck floats. A beach ball floats. A piece of wood floats. Or it can SINK — that means it falls down to the bottom of the water. A rock sinks. A coin sinks. A marble sinks. Some things float and some things sink — but why? Let's find out!