"without water there is no mystery of regeneration"

"the three witnesses in baptism are one: the water, the blood, and the Spirit, for, if you take away one of these, the sacrament of baptism does not stand.  For what is water without the cross of Christ except a common element without any sacramental effect?  And again without water there is no mystery of regeneration [(sine aqua regenerationis mysterium est)].  For 'unless a man be born again of water and the Spirit, he cannot enter into the kingdom of God.'  Moreover, even a catechumen believes in the cross of the Lord Jesus, with which he, too, is signed, but, unless he be baptized 'in the name of the Father and of the Son and of the Holy Spirit,' he cannot receive remission of sins nor drink in the benefit of spiritual grace."

     St. Ambrose, De mysteriis 20, trans. Deferrari (Theological and dogmatic works, FC 44 (Catholic University Press, 1963), 12).  =SC 25, 113, ll. 26-27.  Liturgy of the hours (Universalis):

the three witnesses in baptism – the water, the blood and the Spirit – are one. This means that if you take away one of these the sacrament is not conferred. What is water without the cross of Christ? Only an ordinary element without sacramental effect. Again, without water there is no sacrament of rebirth: Unless a man is born again of water and the Spirit he cannot enter into the kingdom of God. The catechumen believes in the cross of the Lord with which he too is signed, but unless he is baptized in the name of the Father, and of the Son and of the Holy Spirit he cannot receive the forgiveness of sins or the gift of spiritual grace.