"Which sometime were disobedient, when once the longsuffering of God waited in the days of Noah, while the ark was a preparing, wherein few, that is, eight souls were saved by water. The like figure whereunto even baptism doth also now save us (not the putting away of the filth of the flesh, but the answer of a good conscience toward God,) by the resurrection of Jesus Christ " (1 Pet.3:20-1).
Here Peter speaks of the "baptism" which now saves us, and he says that the baptism that saves us is not "the putting away of the filth of the flesh." The following words of Ananias spoken to Paul are in reference to "putting away the filth of the flesh":
"And now why tarriest thou? arise, and be baptized, and wash away thy sins calling on the name of the Lord" (Acts 22:16).
Sir Robert Anderson writes, "The Apostle records the words which Ananias addressed to him (Paul) at his conversion: 'Arise and be baptized, and wash away thy sins, calling on the name of the Lord'...His meaning again is clear: 'Arise and be baptized, and turn away from your evil courses, calling on His name'" (Anderson, The Bible or the Church?, [London: Pickering and Inglis, Second Edition], pp.230-231).
This is in regard to "putting away the filth of the flesh." It is speaking about practical holiness or "perfecting holiness":
"Having therefore these promises, dearly beloved, let us cleanse ourselves from all filthiness of the flesh and spirit, perfecting holiness in the fear of God" (2 Cor.7:1).
From this we can know that the baptism which saves us is not water baptism.
The words "the like figure" are describing a "type". The "water" that bore up the ark and saved Noah is a "type" or "illustration" using things of the physical sphere is teach things in regard to the spiritual sphere.
The Jews would understand that it was the "water" of the flood that bore up the ark and therefore saved Noah and his family. In other words, they were saved by the very thing that brought about death to all the rest of mankind.
So Noah and his family were saved from death by that which brought death. That is also true of the salvation that comes to Christians. For when the believer is baptized into the Body of Christ by the Holy Spirit he becomes one with Christ, even into His death:
"For by one Spirit are we all baptized into one Body...the Body of Christ " (1 Cor.12:13,27).
"Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death? " (Ro.6:3).
Sir Robert Anderson writes, "...the apostle enforces the symbolism of death by declaring that baptism is the antitype of the Flood. The water which overwhelmed the world bore up the ark. Noah was thus saved from death by death; as is the sinner who on believing in Christ becomes one with Him in death" (Ibid., pp.228-229).