According to the Bible, to be baptized in water means to be immersed in water after being born again.
Water baptism is for a person who has been born again.
Those baptized by John the Baptist were completely immersed, as were those who believed in Jesus. Those being baptized went into the water and were completely immersed. Water baptism portrays your sins as being forgiven and cleansed. You are baptized to testify of that cleansing and forgiveness. Jesus had no sin.