Eli5: Why does water expand while freezing, and what would happen if it was frozen in pressurized enviroment/container that cannot expand?

Question

Eli5: Why does water expand while freezing, and what would happen if it was frozen in pressurized enviroment/container that cannot expand?

In: Physics

Answer 1

Interesting to note that if ice didn’t expand and therefore float on water, our oceans would all be frozen as ice would sink to the bottom and not melt much