When new converts were baptised with water they were washed clean. The dirt of their past was washed away. That was the meaning of the symbol used by John and it was still there in the practice of the early church when people were baptised to become Christians. As to the amount and kind of water that was used for the washing, that was not critical. Baptize in the name of the Father and of the Son and of the Holy Spirit, in running water.
Christian baptism is a means of sharing the fire which transforms human lives.
It is a fire that began to be shared with the baptism of Jesus. It continues in the fellowship of the church. In a Church in which we practice infant baptism, we have a separate sign of sharing the Spirit known as Confirmation, but we also believe that by the grace of God children who are made members of the fellowship begin to share in the gift of the Spirit as they grow in faith and take their place in the congregation. That is a place already given to them in their baptism and no second act is necessary although confirmation helps to affirm what God has done. It is because they are already members of the body of Christ that we do not permit any re-baptism.