A lot of time and energy seems to get expended arguing why it isn't necessary to be baptized to be a Christian. How sad. Even a cursory reading of the New Testament will leave the open-minded enquirer in no doubt that baptism was part and parcel of the process in that first century.
Even if there was no other reference to it in the New Testament, the command of the apostle Peter to those first converts in Acts 2:38 to "repent and be baptized" should be the end of the matter.
But of course there are many other references to put the issue beyond doubt. Read through the rest of the book of Acts and see time and again people being baptized as part of the process of becoming a Christian.
The Ethiopian eunuch hears the gospel from Philip and asks "Look, water, what prevents me from being baptized?" (Acts 8:35 ) Obviously Philip's preaching had included the need for baptism.
Saul of Tarsus becomes a Christian after having been a violent persecutor of the faith. The process includes baptism (Acts 9:18).
The apostle Peter, having preached the gospel to some Gentiles (non-Jews) and witnessed the Holy Spirit falling upon them, says "Surely no one can refuse the water for these to be baptized who have received the Holy Spirit just as we did can he?" And he "ordered them to be baptized in the name of Jesus Christ" (Acts 10:47,48)
In Acts 16 Paul preaches the gospel to some Macedonian women. One of them, Lydia, has "her heart opened to respond to the things spoken by Paul and when she and her household had been baptized....." (Acts 16:14,15)
In the same chapter the Philippian jailer cries out to Paul that he wants to be "saved" and asks "what must I do?" Paul tells him to believe in Jesus and takes him "that hour of the night and baptizes him" (Acts 16: 30-33)
The book of Acts is the account of the first people in the then-known world converting to Christianity. Baptism was clearly an integral part of that process. If you wanted to be "saved" you believed, you repented of your sins and you were baptized.
If we're still in any doubt the apostle Peter puts the issue to rest once and for all. Having just described how Noah and his family were physically "saved" through the waters of the flood in the ark, he tells his Christian readers: "corresponding to that baptism now saves you" (!) (1Pet 3:21)
Thats pretty much the end of it, isn't it? It should be - but unfortunately its not. People still want to dispute. They say "what about the man in the desert who is dying and converts but has no chance of getting to water to be baptized. Surely he will be saved won't he?"
There are a million "what ifs". God will deal with the "what ifs". Nothing changes the fact that He instructs us to be baptized.
Ours is not to query God's instructions. Ours is to obey them.
I think we can safely leave the rest to Him.