If you’re really out of water and have only a freezer and a dream, start with a low-saline solution. Brackish water (like from a river mouth) works much better than full-strength seawater. Use a plastic bottle, fill it two-thirds, and freeze it on its side—the ice forms purer near the top.
Pro tip: don’t forget the salt’s depression point. Salt water freezes at a lower temperature than fresh (around -2°C vs 0°C). Your freezer might not be cold enough to freeze high-salt water solid—think of it as nature’s “you can’t cheat me” button. For reference, the Dead Sea never freezes because it’s too salty.
For the survivalist crowd: freezing is a last resort. Burning, filtering, or distilling water is faster and safer. But if you’re stuck in a Cast Away-esque scenario and have time, try building a “frost trap”—a metal bowl placed atop salt water in freezing air will collect pure frost overnight. It’s slow, but it’s yours.
Freezing Salt Water Science Experiment (teacher made)
