I don't know about the rest of the universe, but our comets are supposed to come from the Oort Cloud [1]. The rest of the water needs Hydrogen (The most abunda

I don't know about the rest of the universe, but our comets are supposed to come from the Oort Cloud [1]. The rest of the water needs Hydrogen (The most abundant element in the Universe) and Oxygen (generated by nucleosynthesis in the first generations of stars [2]) [1] https://en.wikipedia.org/wiki/Oort_cloud https://en.wikipedia.org/wiki/Oort_cloud [2] https://en.wikipedia.org/wiki/Nucleosynthesis https://en.wikipedia.org/wiki/Nucleosynthesis