nce you’ve accepted Jesus into your heart, your next step is showing your obedience and symbolizing your rebirth through baptism. The Christian denominations in which I grew up believed that baptism was only valid as a personal decision. Some denominations practice infant baptism or sprinkling, but in the context of what I was taught that practice seems to have no significance whatsoever (except to upset the baby).
The basis for baptism is vague and consists (like most Christian doctrine) of cherry-picked verses scattered throughout the New Testament and inferences from dialog contained therein. This site contains a lengthy discussion on why believers must be baptized and why immersion is necessary. A quick glance tells you right away that the ritual is heavy on symbolism and light on substance. Here’s the gist:
You are “crucified” (standing upright in water), you are “buried” (immersed into the water), and you are “resurrected into life” (raised out of the water).