For most fish, they cannot survive if they are frozen into ice and then melted. Because when the water in the cells is frozen into ice, it turns into tiny ice particles. These small ice particles will puncture the cell membrane and destroy the cells, so even if the ice melts, the fish will still die. This is true for most animals, including fish, amphibians, reptiles, birds and mammals.

But things are not absolute. Some fish survive perfectly well after being frozen, and then revive again when the ice and snow melt. This is mainly due to the special enzymes in the bodies of these fish. When the water in their bodies freezes into ice, these enzymes can work to make the water form finer ice flakes, and the shape of these ice flakes is more rounded. It will not puncture cell membranes, so these fish will be fine when the ice and snow melt.

In addition, the fish that is least afraid of cold in the world is called Big Head Star, which is a type of cod that lives in Antarctica. Its anti-freezing method is even more unique. Generally, fish freeze into "popsicles" at -1°C. This kind of Antarctic cod can live actively at a temperature of -1.87°C. It can freeze without freezing because the blood of this fish contains a component called glycogen, which has a similar effect to a car's antifreeze. This inosose is its unique biochemical substance and is an antifreeze protein. The reason why it can swim around nonchalantly at such a low temperature is because of this antifreeze protein. Its mechanism of action is different from the enzyme mentioned above.

Antifreeze proteins have antifreeze effects because their molecules have expanded properties, as if their structure has a surface area that easily interacts with water or ice, thereby lowering the freezing point of water. This prevents body fluids from freezing. Therefore, antifreeze proteins give this Antarctic cod an amazing ability to withstand low temperatures.