"Baptism by immersion in water by one having authority is the first saving ordinance of the gospel and is necessary for an individual to become a member of The Church of Jesus Christ of Latter-day Saints and to receive eternal salvation. All who seek eternal life must follow the example of the Savior by being baptized and receiving the gift of the Holy Ghost" (1).
In Romans, chapter six, Paul teaches the symbolism behind our form of baptism. However, before we can be baptized and cleansed we must repent and forsake old sins. Baptism is a similitude of death and resurrection in the last days unto the gift of eternal life. Versus three-four state,
"Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death? Therefore we are buried with him by baptism into death; that like as Christ was raised from the dead by the glory of the Father. even so we also shall walk in newness of life".These versus point out to us that the process of our whole bodies being completely submerged under the water at baptism signifies the act of death and burial, just as Christ died and was buried. Rising from the water signifies the resurrection. As Christ was resurrected from his death as a perfected being, we too are raised, clean and pure before God. Mosiah 3:19 speaks about the "natural man" being an enemy to God. Ideally, after baptism this natural man is dead in us. Romans six and seven say, "Knowing this, that our old man is crucified with him that the body of sin might be destroyed, that henceforth we should not serve sin. For he that is dead is freed from sin". The cleansing power of baptism blesses us with a "newness of life" as mentioned in verse four. This "newness of life" leaves us clean and worthy enough to walk in the presence of God, not in the literal sense, but in the sense that we are blessed with the Gift of the Holy Ghost and are open to quiet whisperings and promptings from the Lord. When baptism is meant as a similitude of Christ's death and resurrection, why would it be done in any other way other than as performed by than immersion.
When we choose to follow our Savior's example and be baptized by the proper authority and continuously keep those covenants we made at baptism, we can become the Lords servants and by us will His work be completed on the earth. Verse eighteen says, "Being then made free from sin, ye became the servants of righteousness". Though often times we may be tempted by things of the world and the church standards may seem restricting, it is through them we attain true freedom. The covenants we made with God will bless us continually as we righteous strive to uphold our standard of virtue.
(1) https://www.lds.org/topics/baptism?lang=eng
(2) https://www.lds.org/general-conference/1999/04/spiritual-power-of-our-baptism?lang=eng