Translation:Do you want still water or sparkling wine?
Me either. I grew up in New England. We typically referred to it as 'water'. Most people got their water from a tap back then. If we wanted something else we'd specify. If there was any confusion we said "just plain water". This generally meant, not soda water, not bubbly water, nothing added, not even cubes.
See, now I'm in the Pacific northwest, and the only "Stillwater" I've heard of is the birthplace of one; Leroy Jethro Gibbs. In Washington state we just call it water. If there's anything different about it, Then we just say what's different: it's a bottle of~vitamin water, sparkling water, a trucker's water (um, don't drink from the last one.)
I grew up in NE New York state; I've always used "tap water," though I see how that wouldn't fit as a translation in reference to bottled water. But in English, if I meant non-bubbly water in a bottle, I would just saw "bottled water," which makes me wonder if it's common to qualify the type in French, or if this is just teaching us vocabulary. I've heard "still water" as a phrase, but usually in reference to puddles or ponds, as in water that isn't flowing and so is not safe to drink. "Plain water" is a new one for me, though.
I think it relates specifically to French & Italian restaurants where they always start by bringing water to the table, and give you the choice of sparkling or (Non-sparkling). The Non-sparkling choice has a 50/50 chance of being bottled or just tap. In that context you need a specific word for water which is not sparkling and might or might not be from a bottle.
I have never ordered "still water" but I have seen large bodies of still water. As for ordering in a restaurant, I ask for water. If servers are confused as to what kind of water, they can ask a clarifying question such as, "Bottled or tap?" Almost everywhere I have gone, tap water is implied when the customer doesn't specify a type of bottled water.
It may be the correct translation, but it's not correct English - at least not in context, as demonstrated by the volume of comments here where no native English speaker asks for 'still water' in a restaurant or anywhere else for that matter. 'Still water/s' is a term associated with large bodies of water, as noted above ("still waters run deep").
Exactly! People are hell bent on translating word for word from one language to another and that is NOT how translation works. Languages work in their own quirky way and to force one to be like another is to put square pegs into round holes. In France you will be offered 'de l'eau gazeuse.' Imagine in an English speaking restaurant being offered 'gassy water.' Just brought in from the swamp, I'd guess.