I don't know about qualifications, but what St. John did not say “born of water and of the spirit” Then you might be able to say water relates somehow to our earthly birth and spirit relates only to a spiritual rejuvenation. But we know from Titus 3:6 "he saved us, by the laver of regeneration, and renovation of the Holy Ghost." Just in case you are adverse to water, to laver (or to wash) is done in water. In Judaism "water" is said to bring life, it was said to flow out from the Temple. “For thee my soul hath thirsted; for thee my flesh, O how many ways! In a desert land, and where there is no way, and no water: so in the sanctuary have I come before thee, to see thy power and thy glory." [Psalms 62:2-3]. And we see it again in Psalms 106:35 “He hath turned a wilderness into pools of water, and a dry land into water springs. And in the New Covenant we have John being shown rivers of crystal clear water giving sustenance to the "tree of life", [Apocalypse 22:1].
Given the metaphoric understanding of "water" it is quite clear that it does not represent an earthly birth because the "flesh profiteth nothing." Christ is speaking of a regeneration not two births, one earthly and one spiritual. This should become evident is verse 12, "If I have spoken to you earthly things, and you believe not; how will you believe, if I shall speak to you heavenly things?" [John 3:12].
Baptism, water and Spirit renew our relationship with God. There are two types of sin, the type in which we ourselves volunteer an immoral act; this is called actual sin because the individually actually wills the dastardly deed. We are guilty of another type of sin; we bear the guilt of original sin, as an adult or as an infant simply because we are progeny of Adam.
The original justice accompanying Adam's creation was a moral quality or habit that perfectly joined the will to an enlightened understanding of the will of God. Inexplicably joined to the other cardinal virtues, justice gives the rights to honorable prudence, temperance, and fortitude in moral acts. Prior to his original act of rebellion, God 'abides' in Adam. This abiding is much like we are invited to abide in Christ when partaking in the Eucharist. [Cf. John 6:57]. Christ renews us through the Church with the Grace of Baptism (water and Spirit). The punishment of original sin is the deprivation of original justice that once belonged to our patriarch. All men inherit this one man’s sin being a part of the family of Homo sapiens. Prior to the fall, Adam stood before God as a just man. The original man was created with a soul that was perfectly joined to the intellect and perfectly united with the will of God, overflowing the knowledge of truth; the intellect functioned in the light of God's will disciplining the lower appetites through reason alone. However, because of his unjust act likely born out of the philosophies nominalism, relativism and rationalism, we now bear the guilt for the sin of this one man.
The graces received in Baptism regenerate the soul, making it 'right with God', i.e. righteous. It starts us on a journey from a sate of unjust to perfectly just, "not rightness of knowledge or rightness of action but is rightness of will.” Perfecting, as it we, the state of justice, the movement from the state of unjust to a perfection of justice, a will atone to the will of God. “Justice is uprightness (rectitudo)-of-will kept for its own sake.” [St. Anselm, On Truth, 12].
That was a rather long post, wasn't it? In any event Baptism is a lot more than walking the aisle and confessing one's faith. It is an efficacious grace that begins our journey in the Kingdom of God.
JoeT