Water baptism, in the Name of the Father, Son, and Holy Spirit is a salient ordinance of the Christian Faith. Jesus commanded that His followers submit to baptism as an outward recognition of their spiritual conversion. What's important to understand is the New Testament makes water baptism a post conversion sacrament. That lends tremendous meaning to the essence of water baptism.
First, a post-conversion sacrament teaches that baptism applies only to the redeemed. Nowhere does God command or permit sinners to be baptized.
Two, a post-conversion sacrament teaches that baptism, in no way, effects our eternal destiny. Baptism has no power to cleanse the soul from sin or acquit man from his moral guilt. Salvation is Christ's work of grace, received by faith, and applied by the Holy Spirit. The baptismal ceremony is an outward testimony that Christ's Blood has redeemed us. That's why we understand water baptism to be a confessional sacrament not a transformational sacrament.
Three, as a post-conversion sacrament it visibly interprets the conversion experience. The baptismal participant willingly submits to another immersing him/her, just as sinners submit to Christ for salvation. The plunging into the water illustrates both death to sin and cleansing from sin. The rising from the water represents the Believer's resurrection from the dead into the newness of eternal life.
Those who have been born again, but not baptized in water, should follow Christ's command to be baptized. While water baptism is not transformational, it does bring joy in following the Lord's command.