A man must be born of both to be born again. He is not begotten of the Spirit and born of the water. Let us look at the process of begotten and then being born into the kindom of God. The alien sinner may be begotten by the Word of God. If that Word lodges in a good heart, that person has been begotten by the Word.
Birth is actually a transition from one form of life to another.
A baby is literally delivered in a bag of water. When he takes his first breath of air, he has made the transition from one form of life to another. Similarly, a spiritual transition is made by an alien sinner whe he is begotten by the gospel of Christ and obeys the gospel to be born again. His sins are washed away in baptism, and he is brought to spiritual life through the indwelling of the Holy Spirit. By this birth of water and of the Spirit, the sinner has made the transition from the life as a sinner to the new life as a child of God.