There is this unfortunate thing that happens with water when it freezes—it expands. Freeze a human body and every cell explodes like they’re glass bottles.
And we are mostly made up of water.
How about some additive to water that prevents is from expanding when it freezes. Or maybe some kind of electrical or magnetic force, or EM force? A microwave seems to be a the natural resonance frequency of the water molecule. Can you hold the water molecule in “a state” at or below freezing while applying a microwave source. Seems like you might be able to change the transition point not by adding energy but preventing the water molecule from moving.