1. Because Jesus was baptized that way.
“As soon as Jesus was baptized, he went up out of the water.” (Matthew 3:16a). “As Jesus was coming up out of the water…” (Mark 1:10)
2. Every Baptism in the Bible was by immersion.
For example, “Then both Philip and the eunuch went down into the water and Philip baptized him. When they came up out of the water…” (Acts 8:38–3)3. It demonstrates I am a Believer.
3. The word “baptize” means “to dip or immerse”.
4. It best symbolized a burial and resurrection.
“Or don’t you know that all of us who were baptized into Christ Jesus were baptized into his death? We were therefore buried with him through baptism into death in order that, just as Christ was raised from the dead through the glory of the Father, we too may live a new life.” (Romans 6:3–4)