From Introduction to Theology, page 239 by J. C. Wenger, © 1954 by Herald Press, Scottdale, Pa.:

In 1899 a Christian minister from Pennsylvania (A. D. Wenger) visited the catacombs of Rome. One day he walked out the Appian Way to the catacomb of St. Callistus. “I had been in other parts of this catacomb twice before, but this time I told the guide that I wanted to see frescoes of baptism. Soon we reached one of about the end of the second century where a minister is represented as baptizing a young applicant. The minister stands on the bank and the applicant in the water. A handful of water has just been dipped and put on the head of the applicant where the minister’s hand still rests, perhaps to pronounce a blessing. Small streams of water are plainly seen falling from the head of the applicant. . .
“We went on a little farther to another fresco very similar to the preceding one, and of about the same age, but the minister’s feet appear to be just a little in the edge of the stream and no water is represented as falling from the head of the applicant who is in the water and standing erect.
“We went still farther eastward under the hill and beneath the Appian Way. . . . Here we found the baptism of Jesus by John the Baptist. John stands right at the edge of the Jordan and Christ stands in the water below him. It is also so represented by the picture of it in the museum. Baptism by dipping water on the head with one hand appears to be just completed and John is bending slightly forward with his hand at the elbow of Christ to help Him come ‘up straightway out of the water.’ . . . This is the fresco of baptism that has been assigned by some to A.D. 107.
“I asked the guide to show me some frescoes of other modes of baptism. He said, ‘There are no other modes represented in any of the catacombs.’”

From Water Baptism – The Doctrine of the Mode, pages 14 & 15, emphasis in the original. Written by Rev. W. A. Mackay, B.A., D.D., reprinted by D. W. Friesen & Sons, Altona, Man.)

But in the second and third centuries we find the state of things deplorable indeed. The disposition to ascribe particular virtue to external forms had gone on constantly increasing, until, by-and-by, nude immersions, accompanied with exorcism, anointing, and every species of superstitions, fairly ran riot in unseemingly and scandalous practice. It was thought that there was a saving virtue in the very water of baptism. Just as it was believed that the bread and wine, after consecration, became the real body and blood of Christ, so it was believed that the water of baptism, after the invocation, possessed the real presence of the Spirit. The natural conclusion from this was the the more water the better, and that the water should be applied to the whole body so that the regeneration might be complete. We, therefore, now find trine immersions in a nude state, accompanied with exorcism, unction, the giving of salt and milk to the candidate, clothing him in snow-white robes, and crowning him with evergreens. Remember that there is not one ancient immersion that was not accompanied with these other superstitions. There is precisely the same authority for the immersion as there is for the nudity, exorcism, unction, etc.,—no more, no less.

The first mention of immersion as a mode of baptism, is by Tertullian, and he mentions it associated with all the above practices, and then acknowledges that all these (immersion included) are based on tradition and destitute of Scripture authority. His words are, ‘For these and such like rules, if thou requirest a law in the Scripture, thou shalt find none.’ (See De Corona Militis, chs. 3 and 4)

Thus immersion, as a mode of baptism, came into use.

The following quotes are from A Third Way, by Paul M. Lederach, © 1980 by Herald Press.

Baptism is administered to a believer, not on the basis of what he knows, but as the Scriptures and the historic Mennonite faith indicate, on the evidence of the new life. . .

Concerning baptism, Anabaptists differ significantly from much of Protestantism, as well as Roman Catholicism, not only by not baptizing babies, but also by the importance given to baptism when compared to other practices of the church.

In general, both the Catholic Church (in the mass) and Protestant churches give much more attention to communion than to baptism. However, among Anabaptists baptism had first place because baptism is the critical issue in realizing a regenerate, disciplined church.

Baptism is the tool for gathering a redeemed society, a society of pilgrims, separated from the evil of the unregenerated world.

Baptism is the symbol of discontinuity with the world.

In terms of binding and loosing, some have seen baptism as “binding” and discipline as “loosing.”

At the heart of baptism is a pledge—a pledge to the Father, to the Son, to the Holy Spirit, and to fellow believers to live a pilgrim life of discipleship.

Baptism is a symbol; it is not a sacrament. It is an ordinance, and as an ordinance it is basically a teaching device. But what does baptism symbolize? This has given rise to an unfortunate detour in the life of the church. For some reason, the church has frequently argued about the mode of baptism while often missing its meaning. Historically, there have been two ways to baptize: immersion and pouring or sprinkling.

Actually, neither mode can carry all the symbolism. Immersion symbolizes participation in the death, burial and resurrection of Jesus. The believer is immersed in the water and then raised out of the water. But with immersion has gone many other questions: How is it done? Is the believer immersed forward or backward? Is the believer immersed once or three time?
Pouring symbolizes Pentecost and the pouring out of the Spirit. In pouring, the one to be baptized kneels, and after the water is administered, he is offered the right hand of fellowship. . .
(Pages 81 to 83)

But among the Anabaptists the testimony of the one baptized was not enough. The additional testimony of the congregation was needed. It was not enough for a person to come to the congregation and say, “I have received the Holy Spirit.” The claim had to be authenticated by brothers and sisters, who could say, “yes, we see the work of the Spirit in your life.”

A problem facing the church today is unauthenticated claims of professing Christians.(Page 85). At water baptism there was an oral confession of faith. The one being baptized publicly stated: “I believe in God. I believe in Jesus Christ. I believe in the Holy Spirit. I am sorry for my sins. I promise to live a life of faithfulness to Jesus Christ until death.” In addition to the oral confession of faith and the promise of faithfulness, there was a transaction that today is often ignored. The one being baptized placed himself in the care, discipline and fellowship of the faithful community. But even this was not enough. The congregation also pledged to the one being baptized their love, care and discipline. (Pages 86 to 87)

Some personal thoughts:
• The first Baptists, in both England and America, did not practice immersion. Immersion was introduced in England around 1633 and in Rhode Island in 1644.
• If the Greek word baptizo is taken to mean immersion and only immersion, this introduces a serious problem. Immersion means to place an object under water. It does not include the thought of taking that object out of the water. Some Baptist writers have been honest enough to admit that.
• The fierce emotional attachment of Baptists and others to immersion indicates an underlying fear that one cannot be saved without baptism by immersion.
• A number of the Scriptural uses of the word baptism refer to the baptism of the Holy Spirit at the time of conversion, or to the baptism of blood (opposition and persecution) and not water baptism.
• Baptism is symbolic of that Holy Spirit baptism and also of a separation from the world and identifying oneself with the people of God.