Much more important than water, is the interaction of the new believer's heart with the great Heart of God.
Unless there is a change on the inside, it isn't going to matter a fig how wet someone gets on the outside.
It is that inward baptism...that baptism of the Holy Spirit and fire...(and no, I'm not referring to gibbering in "tongues" or to being "slain in the spirit).
There is One Lord...One Faith...and One Baptism.
Why would someone who is still in their sin even want to be baptized anyhow?
Jesus was baptized. He came to the place where John was baptizing in the Jordan. John seemed a bit reluctant at first, but Jesus prevailed:
Mat 3:13 Then cometh Jesus from Galilee to Jordan unto John, to be baptized of him.
Mat 3:14 But John forbad him, saying, I have need to be baptized of thee, and comest thou to me?
Mat 3:15 And Jesus answering said unto him, Sufferit to be so now: for thus it becometh us to fulfil all righteousness. Then he suffered him.
I like what Jesus says here. He was baptized in order to "fulfill all righteousness". Obviously, He had no sins that needed washing away...but something amazing did happen:
Mat 3:16 And Jesus, when he was baptized, went up straightway out of the water: and, lo, the heavens were opened unto him, and he saw the Spirit of God descending like a dove, and lighting upon him:
Mat 3:17 And lo a voice from heaven, saying, This is my beloved Son, in whom I am well pleased
But it is what happens next that drives me to my knees.
Jesus goes out into the wilderness to confront the Enemy...
Because He showed me the way, I was also baptized...and was raised to New Life.
Which is what baptism is really all about.
You will always have sins that need to be forgiven. The water cannot wash them away.
What it can do is to give you New Life in Christ. You will still be tempted, and you will still sin. But now you have the power to fight back. You have the Holy Spirit. God is in your corner.
And if God be for us, who can stand against us?