Fun idea you got, but not exactly, in some european languages, "sweet water" refers to drinking water, as opposed to what would be "salt water", water from seas and oceans.
Acqua dolce in Italian is literally sweet water opposed to acqua salata, salt water. It's a common mistake to translate literally expressions and grammatical constructs from one's native language to a foreign language. I probably did it this reply without noticing it: it's long enough to contain some bug.