This sounds like a thread from a few days ago. Water (like hydrocarbons) seems to be ubiquitous in the universe. Don’t know why that should surprise me, but I always tended to think of the universe as a debris field of mostly rocks.
It could be that as we pass through space on our way around the sun, that water is being continually added from ice dust in our path.
That’s basically what happens, but these are not just specks of dust, they’re 20 to 30 feet in diameter, and arrive in the millions each year.