There are two common water words in IE: 'water' cognate with Russian (etc) 'voda', Greek 'hudor', Latin 'unda' (wave), and Hittite 'watar-'. In fact the Finnish is very close and is a good bit of evidence that Finno-Ugrian may be closely related to Indo-European.

The other word is Latin 'aqua' (French 'eau'), related to Norse 'a' (modern Scandinavian 'aa') for river, and the element -ay in some English place-names. The Hittite for 'drink' is 'akwa-'. It as has been postulated by some as an extremely ancient word for water found all around the world.