Baptism is the outward expression of an inward faith. It marks a changed life because you have made a decision to put your faith and trust in Jesus. The word "baptism" as it appears in the Bible, means immersion (the process of submersion in water followed by emergence from the water). In ancient times, the word was used to describe ships at sea that had sunk under the water. Even in the New Testament this word is also used for the washing of cups and pitchers.
The New Testament was originally written in Greek. When the Greek word ‘baptizo’ is used in the New Testament, our English word “immerse” fits nicely every time. New Testament scholars agree that the baptism of the Bible is immersion. The following examples from the Bible support that understanding: note the descriptions of the baptisms - "down into the water" and "came up out of the water."
As soon as Jesus was baptized, He came up out of the water (Matthew 3:16).
Then both Philip and the eunuch went down into the water and Philip baptized him.
When they came up out of the water (Acts 8:37, 38) .