Matthew Miller's answer shows that water appears very frequently in John's Gospel. Did John originate this symbol, or was it used by others before him? I am specifically interested in the use of this symbolism in the Hebrew Bible (both in Hebrew and in the Greek Septuagint) and in other early literature with which John may have been familiar.
It could well be that John had access to what is now known as the Community Rule of the Dead Sea Scrolls as it was old enough, dating from the 2nd century BCE.
In the third part it says:
"He shall be cleansed from all his sins by the spirit of holiness uniting him to His truth . . .
And when his flesh is sprinkled with purifying water and sanctified by cleansing water, it shall be made clean by the humble submission of his soul to all the precepts of God."
It does seem as if there was a pre-existing concept that linked water to the spirit of God at least amongst the community of Qumram.
While we all begin in the water of our mothers’ wombs, at creation there were the earth’s and heaven’s waters. Water seems to have been used as a symbol for the Spirit in Genesis and Ezekiel.
Gen 1:1-2, 6-8 1 In the beginning God created the heaven and the earth. 2 And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters. …6 And God said, Let there be a firmament in the midst of the waters, and let it divide the waters from the waters. 7 And God made the firmament, and divided the waters which were under the firmament from the waters which were above the firmament: and it was so. 8 And God called the firmament Heaven. (KJV)
Later the waters from heaven would cleanse the earth via the Great Flood.
Ezekiel also seems to have water as a symbol of the Spirit.
Ez 36:25-26 Then will I sprinkle clean water upon you, and ye shall be clean: from all your filthiness, and from all your idols, will I cleanse you. A new heart also will I give you, and a new spirit will I put within you: and I will take away the stony heart out of your flesh, and I will give you an heart of flesh. (KJV)
John further demonstartes his competency in notarikon in 1 Jo 5:7,8
1Jo 5:6 ¶ This is he that came by water and blood, [even] Jesus Christ; not by water only, but by water and blood. And it is the Spirit that beareth witness, because the Spirit is truth.
1Jo 5:8 And there are three that bear witness in earth, the Spirit, and the water, and the blood: and these three agree in one.
Heaven שמים is the Father מ the Word ם and the Spirit ש and has gematria =3.
Earth ארץ is the Spirit (a secondary metaphor of the aleph: the Spirit hovered over the face of the water when God spoke and created the heavens and the earth.), the water ר, and the blood ץ. Earth ארץ has gematria = 3.
John was proficient in notarikon. It is likely that Jesus taught it in the temple when he was 12. The teachers had 18 years to pervert his teaching, evidenced with the perversion of his teaching with the confrontation concerning the woman with seven husbands. Jesus then called them liars rather than misinformed teachers, because they had perverted his teaching. Eliezer was cast out of Judaism as a heretic, even though his teaching is still one of the most revered. Again it is likely, that he became a Christian. This paragraph is speculation based on circumstantial evidence presented only to show the plausibility of how he derived it from the teaching of the apostles.
Waters is מים . This is creation י in the Father מ and the Son ם.
The shin represents the Spirit which gives life ש
Put the together and you get heaven שמים .
One must be born of the water מים and the Spirit ש to be in 'heaven' שמים.
With this saying, and the others above, it might be argued that John is teaching notarikon.
The Greek church abandoned the use of Notarikon even before they knew it, eliminating the Hebrew text in favor of the Septuagint.
Obviously here, the Hebrew play on words is being expressed in Greek.