I hadn’t thought of that. I see where the frozen saltwater will absorb heat, then go through a phase transformation and maintaining the same temperature until the transformation is complete and its transition temp will be lower than potable water.
Exactly right (and succinctly put).
I should have mentioned that it’s necessary to make sure that your salty water actually freezes. Very salty water freezes at 0*F (that’s how Fahrenheit originally calibrated his scale). If your freezer isn’t set to sub-zero temperatures, you will have to dilute the salt until it actually freezes. If it doesn’t actually freeze, it won’t be very effective.