Cascades to Coast

the fantastic Will

Why does ice float?

For any object to float, it has to be less dense (have less mass for the same volume) as the liquid it is in. This is why say a cork floats in water but a rock does not. When water freezes and becomes ice, it increases in volume and as a result becomes less dense than it was as a liquid. Since it is now less dense than the water it will float.