I'm no physicist but I'm pretty sure oxygen is the most prevalent element on Earth mass-wise, and hydrogen is the most abundant element in the universe, so it s

I'm no physicist but I'm pretty sure oxygen is the most prevalent element on Earth mass-wise, and hydrogen is the most abundant element in the universe, so it seems likely that there are a good number of water molecules that have never existed before, and that most (all?) water molecules will not exist indefinitely. A lake can be a lake but that doesn't mean the water is the same water. In any solution, the bonds of water molecules are being continuously rearranged. The odds that any of the water molecules leaving such a solution have any of the atoms they started with are infinitesimal. For the most part, we live in a giant soup of chemistry on this planet. Everything changes all the time, nothing is forever.