Why does ice float on water?

The answer

Most things shrink when they freeze, but water does the opposite: it takes up about nine percent more room as ice. That makes ice less dense than liquid water, so it floats. As it freezes, water settles into a hexagonal crystal pattern. Floating ice matters for nature too. Because ice floats, ponds don't freeze from the bottom up, and the ice on top keeps the water below from freezing solid, which is lucky for fish. In this case from Matter of Record Files, Maisie asked why her ice cube floated on her drink, and Inspector Fig pushed it down with a spoon. It bobbed straight back up.