How do fish survive in Antarctica's freezing seas?

Antarctic waters are cold enough to challenge most fish, but notothenioid fish have evolved special antifreeze proteins in their blood and body fluids. These proteins bind to tiny ice crystals and prevent them from growing dangerously large. Some species also have reduced bone density, which helps with buoyancy in cold water. This remarkable adaptation allows them to survive in one of the harshest marine environments on Earth. It is one of the best-known examples of evolutionary adaptation to extreme cold.