I'm not sure about what's the problem with slow thawing though: AFAIK most tissues are pretty stable at fridge temperature for a few hours (from 4hours for a heart, up to 36hours for a kidney), but freezing is another matter: the slower you freeze things, the bigger the ice crystal grow, and IIRC you need to freeze things very quickly if you don't want damages from the ice crystal (you want to “vitrify” the water, instead of crystalizing it) and I don't think even liquide nitrogen is enough to freeze big organs quickly enough.

I remember there being research where they successfully froze and then revived hamsters in the microwave (a scientific one to prevent uneven heating though), but it had no hope of working in people or even cats and dogs.

ah yes, the well known "hot pocket" problem - one of the most challenging in cryogenics

> People falling into freezing water, dying, then being revived ours later comes to mind.

Except this doesn't exist, these people don't actually freeze, as in they never go bellow 0, most of them stay well above 0 actually. They're very different phenomenons

For example: https://jmedicalcasereports.biomedcentral.com/articles/10.11...

> A 52-year-old Italian mountaineer, was trapped in a crevasse and rescued approximately 7 hours later by a professional rescue team.... His core temperature was 26.0 °C

or: https://en.wikipedia.org/wiki/Anna_Bågenholm

> her body temperature decreased to 13.7 °C (56.7 °F), one of the lowest survived body temperatures ever recorded in a human with accidental hypothermia.

The body has time to prepare for the cold by making a lot of cryoprotectants in the cells. That of course only works in quite particular conditions and in a liivng host, and the induction would be quite painful. The remaining damage of defrost is fixed later on.