I do not believe that a professing Christian who refuses baptism is a genuine Christian.
Let me first go to Acts 2:38a translated into Portuguese “Arrependei-vos, e seja batizado cada um de vós em nome de Jesus Cristo, para | remissão dos vossos peacados” (DA ERC|DA ERA).
The translation uses the strong imperative for KJV "repent" but the obligatory subjunctive for KJV "be baptized."  The verse as translated is best understood as “You-people-repent-you, and-so let-s/he-be-baptized each one of you in the name of Jesus Christ, in-order-for the remission of you-people’s sins."  We repent for remission of sins, but that repentance obligates us to be be baptized.
Regarding Noah's Flood, 1 Peter 3:21 says “which also after a true likeness doth now save you, even baptism,| not the removal of dirt from the flesh, but an appeal to God for a |clear conscience|), by the resurrection of Jesus Christ” (ASV|NASB|RSV 1952|KJV).  The actual ceremony involving water is excluded from the saving process, but the verse does indicate that the repentance baptism represents is what saves us.  No baptism = no biblical faith/repentance.
I certainly believe that we are saved by faith before baptism on the basis of such passages as Ephesians 2:8-10.  James 2:14-26 and Galatians 5:6 indicate that biblical faith acts, and Ephesians 2:8-10 indicate that a person is saved without works in order for works.  [I believe that an unwillingness to be baptized demonstrates a lack of biblical faith in the Gospel
At Matthew 28:19-20, Jesus said “Go, therefore, and make disciples of all the nations, |bautizad = baptize| them in the name of the Father, and of the Son, and of the Holy Spirit, | enseñad = teach| them to obey everything I have told you| ; and lo, I am with you always, even to the end of the age" (NBV|RVA margin and translated|NBV|RVA margin and translated|ICB|NASB).  The Greek word translated "disciples" is translated "followers" in the ICB.  We make converts, the converts get baptized, and they are taught to follow the things Jesus ordained.  Under these circumstances, I cannot imagine this important step being omitted with the Lord's okay.  A person unwilling to follow Jesus' basic command to be baptized is not ready to follow Him in the subsequent matters.
In Romans 6:2-11, the Christian is pictured as having died to sin and risen to new life in baptism.  Again, a person unwilling to participate in this shunning of sin and with a new life demonstrates a lack of biblical faith in the Gospel.
In the Baptist church I got saved at, baptism was to be a public identification with Jesus Christ.  If so, I do not see how a person unwilling to identify with Jesus Christ could be a genuine follower of Jesus Christ.