Antarctic fish have adapted themselves magnificently to the extreme environment. Antarctic fishes have natural antifreeze proteins in their system which prevents them from freezing. However this anti-freeze is a double edged sword which can have detrimental effect on the animal.
The fishes also known as Notothenioid (ice-loving) fish can make a special kind of protein which are able to attach to the ice crystals in the blood and prevent it from clustering. The downside is that these crystals stay solid even at normal temperatures.