お水だけでけっこうです。

honorific/polite/humble prefix

water (esp. cool, fresh water, e.g. drinking water); fluid (esp. in an animal tissue); liquid; flood; floodwaters; water offered to wrestlers just prior to a bout; break granted to wrestlers engaged in a prolonged bout

only; just; merely; simply; no more than; nothing but; alone; as (e.g. as soon as, as much as); worth

indicates location of action; at; in; indicates time of action; indicates means of action; cause of effect; by; and then; so; indicates continuing action; indicates certainty, emphasis, etc.

splendid; nice; wonderful; delicious; sweet; sufficient; fine (in the sense of "I'm fine"); (by implication) no thank you; well enough; OK; tolerable; reasonably; fairly; tolerably; construction; architecture

be; is