At what temperature is water most dense?

Water is most dense at four degrees Celsius because, as it cools from higher temperatures down to this point, the hydrogen bonds between water molecules allow it to pack more closely together, increasing density. At temperatures above four degrees Celsius, water behaves like most substances; as temperature decreases, density increases. However, as water cools further below four degrees Celsius, the hydrogen bonding causes the molecules to arrange themselves into a more open structure, leading to a decrease in density. This unique property is why ice floats on liquid water. The maximum density occurs precisely at four degrees Celsius, making it a critical point in understanding the behavior of water in natural environments.