Some fish have proteins in their blood that physically stop ice crystals from growing

Fish living in Antarctic and Arctic waters produce antifreeze glycoproteins that bind directly onto tiny ice crystals forming in their blood and body fluids, blocking the crystals from growing larger even at temperatures that should freeze their tissue solid. Unlike car antifreeze, which simply lowers the freezing point of a liquid, these proteins work by physically coating ice crystal surfaces. The same proteins are now being studied for preserving organs and tissue for transplant.

— Wikipedia contributors, Antifreeze protein — Antifreeze glycoproteins in notothenioid fish