I'm a bit confused isn't "en flicka" mean "A girl" and not "One girl". Can anyone please explain and correct me?
It means both, you just have to decide from context which one fits better in English.
Shouldn't this be a woman drinks water? It says it's "one woman drinks water"
vatten is an ett word. This is the kind of word that is usually used as a mass noun of course, but
the singular is ett vatten, vattnet 'a water, the water'
and plural is vatten, vattnen 'waters, the waters'