That baptism was by total immersion is shown by John baptising at Aenon near Salim where there was much water (John 3:23) and Philip going down into the water with the Ethiopian eunuch (Acts 8:38).

Total immersion is the only method of baptism that fully brings out the symbolism of dying to sin and being raised up again to new life in Jesus Christ as referred to by the apostle Paul (Romans 6:1-11; Col 2:12-15).