The Greek word “antitupon,” as used in I Peter 3: 21, is “an adjective, used as a noun,” and denotes, in the NT, “a corresponding type,” being “said of baptism.” “The circumstances of the flood, the ark and its occupants, formed a type, and baptism forms “a corresponding type,” each setting forth the spiritual realities of the death, burial, and resurrection of believers in their identification with Christ.
It 's not a case of type and antitype, but of two types, that in Genesis, the type, and baptism, the corresponding type.” Noah was saved by the ark “through (via) water.” Water was not the means of their salvation, but the ark. The ark is what both delivered and preserved them, the two aspects of “salvation.” Their “salvation” was typical of the salvation promised to the Christian. It pictured it. So also does Christian baptism picture the death, burial and resurrection of Christ.
By saying, "not the removal of dirt from the flesh, but an appeal to God for a good conscience -through the resurrection of Jesus Christ," Peter guards against saving power to the physical ceremony itself.