We only have models, not knowledge
We know that water boils at 100 degrees Celsius, right? Or not ; on mount Everest the water boils at around 70 degrees Celsius, so you can't even boil an egg . Ok, we have a more complex model that links the boiling temperature with pressure, but even that model is not exact at any given pressure. On some temperatures, our linear models fail, for example water cooled below 4 degrees Celsius will not continue to get denser, but it will actually expand, allowing the cold water to float on the surface until it becomes ice. In general, lower temperature would predict lower density in substances. There is nothing in the common physical laws that would predict such anomaly in water, while we can later construct even more complicated models to explain what is happening with water.