Where is the scripture that says it must be done by full immersion? There is no protocol outlined.As I've heard it, "baptism" is a word that, for whatever reason, was not translated during the translation. If it had been translated instead of transliterated, the translation would be "immersion."
So, what you're asking is sort of like asking, "Where is the Scripture that says 'repent' means to turn away from sin?"
For lack of time, I submit the following from another source:
"But immersion is not the only meaning of
baptizo [in Greek]. Sometimes it just means washing up. Thus Luke 11:38 reports that, when Jesus ate at a Pharisee’s house, "[t]he Pharisee was astonished to see that he did not first wash [
baptizo] before dinner." They did not practice immersion before dinner, but, according to Mark, the Pharisees "do not eat unless they wash [
nipto] their hands, observing the tradition of the elders; and when they come from the market place, they do not eat unless they wash themselves [
baptizo]" (Mark 7:3–4a, emphasis added). So
baptizo can mean cleansing or ritual washing as well as immersion."
http://www.catholic.com/library/Baptism_Immersion_Only.asp