Baptism doesn’t make you a believer - it shows that you already believe. Baptism does not "save" you, because you are saved by grace through faith in Christ. Baptism is like a wedding ring – it is the outward symbol of the commitment you make in your heart.
What this means is that those who become Christians become new persons. They are not the same anymore, for the old life is gone. A new life has begun.
Corinthians 5:17 (NLT)
For we died and were buried with Christ by baptism. And just as Christ was raised from the dead by the glorious power of the Father, now we also may live new lives.
Romans 6:4 (NLT)
For it is by grace you have been saved, through faith-and this not from yourselves, it is the gift of God - not by works, so that no one can boast.
Ephesians 2:8,9 (NIV)