What would happen if water couldn't expand when freezing?

Suppose water was sealed in a box that wouldn’t expand with the water as it froze. Would the ice be extra dense? Would it freeze at all?

If water were enclosed in a container of sufficient strength, which did not expand itself under temperature decrease, it would remain liquid at the temperature at which it normally becomes solid. It would become a supercooled liquid. When pressure was released, the water would expand, and freeze.

Freezing temperature varies with pressure but in order to increase pressure there would have to be some crystalization. Lower the temperature enough and it would still freeze. With even more pressure you actually get a different type of ice crystalization.

And, as with the boiling water in the unbreakable airtight box, opening it up to take a peek isn’t recommended.