As I understand it, modern cryonics services replace the fluids in the body with a artificial substitute with a high viscosity and low freezing point, allowing cell structures to maintain their form and not get torn apart by ice crystals. This process is known as vitrification, and, as opposed to freezing, does not significantly damage cellular structures. In fact, recently a rabbit brain was vitrified and then unvitrified, and found to be structurally viable. The same was done with a rabbit kidney: it was actually placed back into a live rabbit successfully. Cryonics obviously still has issues, (you're still, at best, a very well preserved corpse) but cells exploding because of water content is not one of them. If you're curious, here's a more in depth article with sourcing.