When repentant believers are immersed in water, God places them into union with Christ, into union with His death, burial, and resurrection, and into union with the one body of Christ (Rom. 6:3-6; I Cor. 12:13; Gal. 3:26-29; Col. 2:11-13). The passages I have just cited also tell us about other things God does at the time of baptism. Please read them and see, and remember Acts 2:38 as well.
According to this post, if the repentant believer dies before he is immersed in water, God will not place him into union with Christ. That is heresy. And I don't use that word very often.