You will be His witnesses to all men of what you have seen and heard. And now what are you waiting for? Get up, be baptized and wash your sins away, calling on his name. Acts 22:15-16
Simply put, baptism is an outward display and celebration of your inward decision to trust Christ with your eternity. It's an act of obedience, a step of acknowledgment that is representative of the fact that Jesus died on the cross, was buried and walked out of the grave, alive, so each of us can have eternal life.
When you step into the water, you are letting the world know that you have walked into a new life of faith in Jesus Christ and that you are committing to follow Him down a new path. If you've made the decision to follow Jesus, baptism is the next step in your spiritual growth.