Does "Baptism" Require Full Immersion?
Let us start by looking at a scriptural passage which specifically mentions "baptism" but not necessarily in the way Christians are accustomed to hearing it.
"And when they come from the market, except they wash, they eat not. And many other things there be, which they have received to hold, as the washing of cups, and pots, brasen vessels, and of tables." (Mark 7:4 KJV)
Let's look at that passage again with the Greek words for "wash" and "washing" inserted:
"And when they come from the market, except they baptizo, they eat not. And many other things there be, which they have received to hold, as the baptismos of cups, and pots, brasen vessels, and of tables." (Mark 7:4 KJV)
Now a quick look at the context, verses 1-3, shows the connection of washing one's hands and feet. Certainly we are not requiring a full bath everytime one returns from the market! Yet in verse 4 the word we use for "baptism" is used! Now certainly one can and probably does immerse cups and pots, maybe even brasen vessels, but certainly one does not take their table (or "kline" - a couch for sleeping, sitting or eating) out to the backyard swimming pool to immerse it every time it needs cleaning)! So clearly simply the use of the word for "baptism" does not imply full immersion. Granted, many - perhaps even most of the early baptisms were by full immersion - but the point is it need not be full immersion to be baptism.
What is the significance of the Sacrament of Baptism?
Baptism is the cleansing of the soul from Original Sin, and this is why St. Peter says:
"Whereunto baptism, being of the like form, now saveth you also: not the putting away of the filth of the flesh, but, the examination of a good conscience towards God by the resurrection of Jesus Christ." (1 Peter 3:21 DRB) Baptism does not clean the flesh, it cleans the soul. As already established, baptism means "to wash" so we must consider what is washed through baptism. If it is not the filth of the flesh, then it must be the filth of the soul, which would be the Original Sin we have all inherited. St. Paul says: "But not as the offence, so also the gift. For if by the offence of one, many died: much more the grace of God and the gift, by the grace of one man, Jesus Christ, hath abounded unto many." (Romans 5:15 DRB) So we must consider the salvific effect of the Sacrament of Baptism, especially since St. Peter in Scripture tells us that "baptism... now saveth you also."
In many parts of the Holy Land and throughout the Middle East there is no running water, and often where there is running water it was not deep enough to fully immerse someone. Thus sprinkling or pouring of water was used.
Most Christians would agree that the use of water is necessary for baptism, it is the "outward sign" of the Sacrament. Now since it is not the cleaning of filth from the flesh - is the amount of water really the issue? The soul is of the spirit of man, and thus that which is made clean through baptism is the spirit, not the flesh. It makes no sense to insist that immersion is the only valid form of baptism when it really matters not how wet ones flesh gets - but that one has submitted to the Will of God and has been baptized according to His Word, in the Name of the Father, the Son and the Holy Ghost.