"The elephants drink water."
Translation:הפילים שותים מים.
Is there a plural for water in Hebrew and would this be an appropriate place to use it?
Is there a time when you'd use water in the singular? (And if so, what how would you say it?)
"Water" in Hebrew is a bit of a complicated case. It only has one form for both "plural" and "singular" if you can really call them that.
In the distant past, before Hebrew writing came about, and judging by cognates in other Semitic languages, perhaps the singular of "water" was ma' or may (rhymes with pie). Nowadays there is only מים. It's a form called זכר רבוי, a masculine gender word which is always in the plural form.
It's actually quite similar to how in English we always say "clothes" and "pants/trousers", never "clothe", "pant/trouser" (unless you're a tailor and have to talk about each leg of the trousers). And glasses (spectacles) are not made up of one "glass" + one "glass", they're simply "glasses".
Even in English "water" is not like a standard countable noun. It's uncountable. You can't say "two waters" (ok, in practice this rule is broken, because in effect people say it, dropping out the quantifier, when they actually mean "two bottles of water" or "two glasses of water", so it's non-standard). So if someone were to do the same in Hebrew (שני מים/מים אחד), it would be understood according to the context, שני בקבוקי מים, כוס מים אחת etc. It doesn't sound good though, so I would avoid saying anything like that and always use the quantifier.