Noun
Someone who drinks water, especially in preference to alcoholic drinks; a teetotaler. [from 15th c.]
(Christianity, obsolete) A member of an early Christian sect which drank water instead of wine during the Eucharist. [16th–19th c.]
(now historical) Someone who drinks the waters at a spa. [from 17th c.]
Source: en.wiktionary.orgwater-drinker