I don’t know about where water came from but I think a lot that claims to be science isn’t really.
Here is a definition of science
“the systematic study of the structure and behaviour of the physical and natural world through observation, experimentation, and the testing of theories against the evidence obtained.”
So for something like gravity scientists can observe things fall to the ground experiment how fast they fall in different medium, experiment how it works with objects other than earth (two heavy suspended objects will be attacted to each other very slightly, objects fall slower on the moon) come up with a theory and do repeated experiments to test the theory.
For something like where water comes from you can observe but you can not experiment to test theories. The result is scientists have axioms of fundamentals that they think are indisputable, they then observe and draw hypotheses which match there observations and fit in with their axioms, it takes a huge amount of evidence to move the away from their axioms, until the 17th Century those axioms based on an (incorrect) interpretation of the bible was the universe revolved around the earth, Galileo observed the movement of the planets and came to the conclusion that the universe revolved around the sun and received great opposition for stating that, now that has also been disproved.
Another example is how different forms of life appeared on earth.
The majority of evolutionary scientists have as an axiom that there is no God. They observe the variety of life on earth, natural selection (creatures better adapted to their environment survive longer and are therefore more likely to reproduce) and mutations and conclude that all life evolved from the simplest microrganism through these methods (grossly simplied)
There are a small number of “creation scientists” whose base axiom is the bible is the word of God and contains no errors. They observe the same evidence but conclude natural selection doesn’t create new genetic information it only changes the proprotions among the population, different breeds of dog can be created through (unnatural) selection but you skill have the canine kind, they observe that the human eye is vey similar to the eye of an octopus but the rest of the bodies are so different they could nave the same evolutionary ancester and come to the conclusion that natural selection only occurs within “kind” and similarities between different kind are due to having the same designer / creator.