In the Gospel we see John the Baptist baptizing in the Jordan. The way that I had it described to me was that John would be standing in waist deep water out from shore, and the people wading out to him would be calling ot their sins as they came. The actual baptizing was more like dunking the person. It was a humiliation the person underwent in punishment for their sins.
Ancient documents described First ans second Century Christin baptisms as quite a different way. For one thing, they only baptized in Holy Saturday when they were picturing the crucified Jesus lying in his tomb. The y would have dug and filled a six by three pool, that they saw as taking the place of the tomb of Jesus.
The candidate for baptism would ask to have his or her sins taken away in exchange for their entering this tomb of Jesus, dying to sin with Jesus.