The explanation is that water behaves unlike almost any other known substance.
The vast majority of materials condense and gain weight when they cool. Water, on the other hand, only condenses until it reaches a temperature of 4 degrees.
Then it expands again and becomes lighter. Since the temperature of ice is usually zero degrees, it is lighter than the surrounding water, which is just above freezing, and as a result, the ice floats on top.
The fact that water behaves in a special way around the freezing point further means that the layer of ice on the surface acts as a kind of insulator against the water below.
This leads to the fact that the ice layer is generally no thicker than one meter and as a result animals that live in water can survive extremely cold and long winters.
If water did not have these properties, the ice would sink and lakes and oceans would slowly freeze to the bottom, eventually leaving only shallow water at the top.
It can be assumed that the Earth’s climate would then be completely different, which would certainly have affected the ability of life to develop in water.
It is not out of place to mention the fact that water expands when it cools and freezes, but many people have had the experience of sticking a soda bottle in the fridge and finding it cracked, and frozen water pipes are a well-known phenomenon.
