Baptism 4

Quoting from a Lutheran Commentary on the 1 Peter 3:21 passage, the counterpart to Noah's salvation story.

"Kretzmann's Popular Commentary"
The apostle now makes a splendid application of this incident: Which now saves also us as Baptism, its counterpart, not the removal of the dirt of the flesh, but the pledge of a good conscience toward God, through the resurrection of Jesus Christ. The words of the apostle are so simple and so clear that the deliberate  misunderstanding of their import by a great number of Christians is a mystery. Water is to us Christians a  means of salvation. It is water that saves us, that transmits to us the salvation of Christ in Baptism, which is the antitype or counterpart of the Flood, as Peter has just shown. This salvation, of course, does not consist in washing off the dirt which may have gathered on the skin of the body, but it cleanses the heart of sins; it is a pledge, a contract of a good conscience toward God; it guarantees to us that we may have, by virtue of its application, a clean conscience before God, thus being enabled to lift up our eyes to Him without the slightest trace of fear. This is true because the spiritual gifts and blessings which are the result of the resurrection of Christ, the certainty that God has accepted the sacrifice of His Son and granted forgiveness of sins to the  whole world, are transmitted to the believer in Baptism. Thus all Christians are, by reason of their baptism, happy and blessed people, having the certain hope of eternal life through the grace of God in Christ Jesus which they received in the water of Baptism."

The link below discussing what Historical Reformed (Calvinist) beliefs have been regarding baptism.  I'll simply toss some quotes after:
http://www.hornes.org/theologia/rich-lusk/baptismal-efficacy-the-reformed-tradition-past-present-future

Martin Bucer, Calvin’s mentor, wrote the following in his 1537 liturgy for infant baptism: “Almighty God, heavenly Father, we give you eternal praise and thanks, that you have granted and bestowed upon this child your fellowship, that you have born him again to yourself through holy baptism, that he has been incorporated into your beloved son, our only savior, and is now your child and heir…”

This, then, is the point: God blesses us in baptism with new life, though baptism itself does not guarantee perseverance. Thus, we must combine the waters of baptism with enduring faith (cf. 1 Cor. 10:1-12). If not, the heavenly waters God has poured out upon us will drown us in a flood of judgment

What is different, it seems, is that the higher views of baptism are now more out of favor than ever. If we categorically reject “baptismal regeneration,” it must be acknowledged that we have moved significantly away from some traditional Reformed formulations.

Baptism has been watered down (pun intended) from a means of sovereign, saving grace, to a means of granting external privilege.

The importance of baptism to one’s identity as a child of God can never be overestimated. In baptism, we are enfolded into the family of God and begin our enculturation in the life of the eschatological kingdom. In baptism, God unites us to his Son and pours out his Spirit upon us. He weds us to Christ and ordains us to his royal priesthood. He forgives our sin and grants us new life. As the WSC teaches, baptism is not a mere picture, but an effectual means of redemption.

True, baptized persons can renounce their Father and become prodigals; they can reject Jesus as their  husband and become adulterers. Baptism is an act with eternal consequences for the faithful and the unfaithful, and covenant members who renounce their baptismal identity and fall from grace can only expect God’s  harshest judgment (cf. Gal.5:4; Heb. 10:26ff). But apostasy is never our expectation for the baptized. Baptism itself is blessing through and through; indeed, it is the gospel in liquid form.