A helpful way to understand this, perhaps, would be to speak of these symbols as a set of patterns and associations. By this I mean that Biblical symbolism is not a code. It is, instead, a way of seeing, a perspective. He was offering her eternal life. It is to think that Biblical symbolism is primarily a puzzle for us to solve.
Water is a special code-word which means eternal life.
In a general sense, of course, we know that water is associated with the Spiritual refreshment and sustenance of life which comes through salvation. But the Biblical associations with water are much more complex than that. This is because understanding Biblical symbolism does not mean cracking a code. It is much more like reading good poetry. Instead, it is meant to be read visually.