While I'm on a roll as far as pointing out the obvious, ha. I need to explain something about the sacrament of Baptism.
I was actually surprised when I learned some time ago that some Christians misunderstand and vehemently oppose Catholic infant baptism. Actually, I was shocked and boggled by the level of hostility and misunderstanding.
John the Baptist baptized adults because - duh - he was preaching to adults. Christianity did not exist yet. John the Baptist announced the coming of Jesus and remember Jesus explained that John the Baptist was the greatest of the children born to man. John the Baptist was the man who prepared the way for Jesus. As such he articulated the need for a baptism of water. He preached to adults who were Jews. He baptized adults. I mean, think about it. Was he going to say, "I'm not going to baptize anyone until Jesus proclaims the Kingdom, and then I'm going to wait with baptism until new babies are born, and those of you who are adults, sorry, but I'm not going to baptize?" Obviously John the Baptist initiated what would become the first sacrament of ALL BORN IN THE FAITH AFTER THE ARRIVAL OF JESUS CHRIST.
So the fact that "baptism of infants is not in the Bible" is a non sequitur. John the Baptist, through the inspiration of the Holy Spirit, recognized that baptism by water into the faith that would become Christianity would be the hallmark of the faith. You will know they are Christians because they are baptized into the faith.
In those times children were brought up in the faith of their parents. We did not "wait around" to see if someone would "accept Jesus" or "accept Moses" when they were adults. Children were Jews AT BIRTH TO JEWISH MOTHERS. They didn't decide they had a Jewish mother when they had a "temple call" or a "conversion experience" where they "accepted Moses as their Old Testament savior sent by God." Jewish baptism was being born of the womb of a Jewish mother.
Likewise Christians became Christians at BIRTH to CHRISTIAN PARENTS. They were baptized at that time. Obviously John the Baptist couldn't wait for the "first crop" of Christians because he was creating the path by which Jesus would walk and proclaim the Kingdom. When Jesus was baptized by John the Baptist Jesus was showing that no longer was the being born of the womb of a Jewish woman the baptism of a Jew, but that the water baptism of an infant (symbolized by Christ officially "starting his ministry" with his own baptism) would be the declaration of a Christian baby, just as had the birth of a child (and circumcision of a male) was to a Jewish woman.
"Original baptism" was emerging from the womb of a Jewish woman at birth. This was how a Jew was known. John the Baptist declared that a Christian (not yet called that, but one who believed when the Messiah arrived) would be known by baptism. Just as Jews were Jews at birth and did not wait for "an altar call to Moses" so were the first Christians made Christians at birth and by baptism of water.
I hope this helps clear up some surprisingly fuzzy thinking.