Let’s take somewhat of a different slant on this answer.
Let’s talk about marriage.
Is a marriage ceremony necessary for marriage?
Genesis 24:67 (KJV) - And Isaac brought her into his mother Sarah's tent, and took Rebekah, and she became his wife; and he loved her: and Isaac was comforted after his mother's death.
For a more complete read of this beautiful love story, I would recommend reading the entire chapter of Genesis 24.
The point here is that the minute he saw her on the donkey he took her into his mother's tent and the marriage was consummated.
There was no marriage ceremony.
This does not suggest that there shouldn't be a marriage ceremony...
John 2:1-2 (KJV) -
1 And the third day there was a marriage in Cana of Galilee; and the mother of Jesus was there:
2 And both Jesus was called, and his disciples, to the marriage.
...but that such is not necessary to commence a marriage.
While not part of this topic I believe it important to extrapolate forward that sexual union outside of the marital bed actually results in multiple marriages taking place today which is directly contrary to what the Bible counsels.
1 Timothy 3:2 (KJV) - A bishop then must be blameless, the husband of one wife, vigilant, sober, of good behaviour, given to hospitality, apt to teach;
Mark 10:8 (KJV) - And they twain shall be one flesh: so then they are no more twain, but one flesh.
See, marriage takes place within the heart of the people involved not at the altar. The alter is an outward display of an inward commitment.
What does this all have to do with baptism?
Everything.
Luke 23:43 (KJV) - And Jesus said unto him, Verily I say unto thee, Today shalt thou be with me in paradise.
This was said by Jesus Himself to the thief on the cross who repented and turned his heart to the Lord. There would not be a great deal of time for baptizing the thief and yet the words of Jesus were clear.
Why?
Because the thief had been renewed in his heart.
Would it have been good for the outward display of baptism for an inward commitment already made?
Sure, but as in the case of the dying thief or a death bed conversion, that is not always possible.
The agape loving Father and His only begotten Son, Jesus Christ are not up in Heaven with a checklist in their hands.
- Romans Road of Salvation - check
- Sinners Prayer - check
- Baptism - che...
Seriously, they want each of us in Heaven more than any of us even wants to be there. They are looking for a transformed heart not the correct documentation on a passport card.
If one has time for baptism and that by immersion then by all means. However, if one does not have such time then that does not stop them from being baptized else what Jesus told the thief on the cross was a lie.
If Jesus lied on the cross then He sinned even upon the cross of crucifixion.
Exodus 20:16 (KJV) - Thou shalt not bear false witness against thy neighbour.
If that is the case then we are without a spotless lamb who is able to take away the sins of the world.
1 Peter 1:18-21 (KJV) -
18 Forasmuch as ye know that ye were not redeemed with corruptible things, as silver and gold, from your vain conversation received by tradition from your fathers;
19 But with the precious blood of Christ, as of a lamb without blemish and without spot:
20 Who verily was foreordained before the foundation of the world, but was manifest in these last times for you,
21 Who by him do believe in God, that raised him up from the dead, and gave him glory; that your faith and hope might be in God.
That very lie would thus give Christ the blemish and cause the faith and hope of our salvation itself to crumble.