There is a double figure here. The
 flood symbolizes baptism, and 
baptism symbolizes salvation.
The text of 
1 Pe 3:20-21 reads: ". . .
the longsuffering of God waited in the days of Noah, an ark being prepared in which a few, this is eight souls, were quite saved through water. Which figure (baptism is a figure/symbol of Christ's death, burial and resurrection which saves) also now saves us, that is baptism, not a putting away of the filth of the flesh, but an answer of a good conscience toward God through the resurrection of Jesus Christ."
The flood symbolized baptism which 
baptism symbolizes Christ's death (judgment), burial and resurrection which saves.
The 
flood is a 
symbol of 
baptism in that in both instances the water that spoke of
 judgment (in the flood, the death of the wicked; in baptism the death of Christ and the believer, 
Ro 6:2-4) is the water that 
saves.
Baptism is a 
symbol of 
salvation in that it 
depicts Christ's death, burial and resurrection and our identification with him in these experiences.
"Also now saves us," in the context of the 
rest of the NT, means saved by what baptism 
symbolizes--Christ's death and resurrection (
Ro 6:2-4).
This using of the 
symbol to refer to the 
reality is, as I understand it, what the Catholic church calls "sacramental union."
"answer of a good conscience toward God" is a commitment on the part of the believer in all good conscience to make sure that what baptism symbolizes in 
Ro 6:2-4 will become a reality in his life; i.e., that 
as Christ died for sin, so the believer will die to sin.