The flood was a symbol of baptism, yet it was not the flood that literally saved Noah and his family, but the
ARK (Hebrews 11:7). Just as baptism itself does not literally save believers, but is a symbol of salvation in that it depicts Christ's death, burial and resurrection and our identification with Him in these experiences. In reality, believers are saved by what baptism symbolizes--Christ's death, burial and resurrection.
In verse 20, Peter had just spoken about the ark and goes on to say that there is a like figure, or a similar figure, which is baptism. The Greek word for "figure" is "antitupon." Vine, in his Expository Dictionary of New Testament Words, defines the word as "a corresponding type." He says, "It is not a case of type and antitype but of two types, that in Genesis, the type, and baptism, the corresponding type." (Vol. 2, page 96). Cremer's Lexicon says the word signifies an "image or similitude." Thayer's Lexicon defines it as "a thing resembling another."
Dr. Kenneth Wuest, author of Word Studies in the Greek New Testament explains. "Water baptism is clearly in the apostle's mind, not the baptism by the Holy Spirit, for he speaks of the waters of the flood as saving the inmates of the ark, and in this verse, of baptism saving believers.
But he says that it saves them only as a counterpart. That is, water baptism is the counterpart of the reality, salvation. It can only save as a counterpart, not actually. The author is merely using them as an illustration of the use of the word 'counterpart.'
So water baptism only saves the believer in type.
Jesus did not get water baptized for the same reason that we get water baptized, so your argument is moot. All of God's righteous requirements for the Messiah were fully met in Jesus. This act of baptism on His part was a necessary part of the righteousness He secured for sinners. His perfect righteousness will be imputed to those who
BELIEVE (Romans 4:4-6; Philippians 3:9). Water baptism is a work of righteousness and we are not saved by "works of righteousness" which we have done. (Titus 3:5)
As Greek scholar AT Robertson points out about baptism - "a symbol is not the reality, but the picture of the reality."
Baptism is an action which is a work and we are saved through faith, not works (Ephesians 2:8,9; Titus 3:5; 2 Peter 1:9).
The pledge is as an inward, spiritual transaction between God and the individual, a transaction that is
symbolized by the outward ceremony of water baptism. The symbol can be used to refer to the reality and that seems to be what is confusing you. A FLOOD OF CONFUSION. There is no grammar hanky-panky here, just a failure on your part to understand.