When the water in cells freeze they cause massive damage to the cells just like if you froze a jar of water and had the expansion crack the glass. This is the big hurdle that cryogenics is having trying to freeze people right after they die so that they can be thawed out and revived some day in the future when medical technology has improved. At least that is my understanding of the situation. I’d be interested to hear how those certain species of frogs are able to be frozen without their cells being damaged, sounds interesting.