Question:  What "Mode" of water baptism was practiced by John the Baptizer?  By the Lord's disciples during His ministry on earth?  By the believers during their ministry after the day of Pentecost?

Answer:  If it were possible to provide an irrefutable answer to this question, the many disagreements seen in "Christendom's great house" would have disappeared long ago.  However, here are a couple of thoughts for the consideration of "Bereans."  First, the pro-immersion arguments:

The Greek word baptizo, to baptize, and baptisma, baptism, are derived from the word bapto, translated "dip" in Luke 16:24; John 13:26; and Rev. 19:13.

Baptizo, (in form a frequentative or factitive of bapto, dip or dye.)  baptizo to make a thing dipped or dyed.  To immerse for a religious purpose, may be traced back to the Levitical washings, see Lev. xiv. 8, 9; etc., (out of which arose the baptism of proselytes), which were connected with the purification which followed on and completed the expiation from sin.  What was unusual in John's baptism was, that he performed the baptizein on others, whereas under the law each one accomplished it for himself.  Baptism of John was the Baptism of repentance, see Mark i. 4; Luke iii. 3; Acts xiii. 24; xix. 4, and Christian Baptism is Baptism of Faith, see Acts xix. 4, 5.  The difference lies not in the Baptism, but in the relation thereof to Jesus Christ.  By Baptism therefore we must understand an immersion, whose design like that of the Levitical washings and purifications was united with the washing away of sin.  (See "Cremer,") - (A Critical Lexicon and Concordance to the English and Greek New Testament, by Ethelbert W. Bullinger, D.D., The Lamp Press Ltd, p. 80)

As to these Levitical washings, translators variously render the word in Leviticus 14,  as "wash" or "bathe."  When a leper was healed of his disease, he still required ceremonial cleansing according to the Levitical law. 

"And he that is to be cleansed shall wash his garments, and shave all his hair, and bathe* in water, and he shall be clean. . . ." (Lev. 14:8)

* i.e. the whole body.  (footnote in J. N. Darby's "New Translation")

Thus, the case for "immersion" or "dipping" as the mode of water baptism appears to be answered.

But, not quite so fast!  The best way to determine the meaning or significance of a word is to see how it is used in the scriptures, not how the word etymologically evolved from a Greek root.

One point to consider is, 'Was there enough depth of water available in the desert wilderness to totally immerse a healed leper?'  To bathe the whole body does not necessarily mean to "immerse" it.  Today's bath tub is seldom filled to the point where 'total-body immersion' is possible, yet it is possible to wash the whole body.

A second question:  Although baptizo, to baptize, and baptisma, baptism, are derived from the word bapto, which means to dip or dye, the usage of a word, not its derivation, controls its meaning.  Consider that the Jews practiced water baptism by ceremonially washing their hands prior to eating.  This ritual was performed by pouring water over one's hands to flush away any ceremonial uncleanness that might have contaminated them during their exposure to the world.:

     "Then came together unto him the Pharisees, and certain of the scribes, which came from Jerusalem.
     "And when they saw some of his disciples eat bread with defiled, that is to say, with unwashen [aniptos], hands, they found fault.
     "For the Pharisees, and all the Jews, except they wash [nipto] their hands oft, eat not, holding the tradition of the elders.
     "And when they come from the market, except they wash [baptizo], they eat not. And many other things there be, which they have received to hold, as the washing [baptismos] of cups, and pots, brasen vessels, and of tables.
     "Then the Pharisees and scribes asked him, Why walk not thy disciples according to the tradition of the elders, but eat bread with unwashen [aniptos] hands?" (Mark 7:1-5)

     "For laying aside the commandment of God, ye hold the tradition of men, as the washing [baptismos] of pots and cups: and many other such like things ye do." (Mark 7:8)

     "And as he spake, a certain Pharisee besought him to dine with him: and he went in, and sat down to meat.
     "And when the Pharisee saw it, he marvelled that he had not first washed [baptizo] before dinner.
     "And the Lord said unto him, Now do ye Pharisees make clean the outside of the cup and the platter; but your inward part is full of ravening and wickedness." (Luke 11:37-39)

But if "baptism" is a "dipping," how much of the body was dipped? "Dipping" is not the same as "total-body-immersion."

• In the parable of Luke 16:24, the rich man asked:  "Father Abraham, have mercy on me, and send Lazarus, that he may dip [bapto] the tip of his finger in water, and cool my tongue; for I am tormented in this flame."  (Only the "tip" of his finger was requested to be dipped).
• As to identifying the traitor, the Lord said: "He it is, to whom I shall give a sop, when I have dipped [bapto] it. And when he had dipped [embapto] the sop, he gave it to Judas Iscariot, the son of Simon." (John 13:26)  (Did the Lord completely "immerse" the sop?  If so, he would have gotten the sauce all over his fingers.  The evident meaning, for those who have dipped tackos in salsa at a Mexican restaurant, is that he partially dipped the "sop.")
•  And, was the Lord's entire garment fully dyed with the blood of His enemies, or only a corner of it?  "And he was clothed with a vesture dipped [bapto] in blood: and his name is called The Word of God." (Rev. 19:13)

        Finally, but more significantly, there is an interesting connection made between the "baptism" of John, and the "baptism" of the Holy Spirit. John baptized (ceremonially washed) repentant sinners.  He directly connected his water baptism to the baptism of the Holy Ghost to be performed by the Lord Jesus Christ.

     "I indeed baptize [baptizo] you with water unto repentance: but he that cometh after me is mightier than I, whose shoes I am not worthy to bear: he shall baptize [baptizo] you with the Holy Ghost, and with fire." (Mat. 3:11)

        Did John baptize by sprinkling or pouring water upon sinners, or did he baptize by totally immersing each sinner beneath the surface of the water?  Since John's water ritual prefigured the Lord's baptism with the Holy Spirit, one would expect the mode of John's baptism to be identical with the mode of the Holy Spirit's baptism.

     "And when the day of Pentecost was fully come, they were all with one accord in one place.
     "And suddenly there came a sound from heaven as of a rushing mighty wind, and it filled all the house where they were sitting.
     "And there appeared unto them cloven tongues like as of fire, and it sat upon each of them.
     "And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance." (Acts 2:1-4)

     "And it shall come to pass in the last days, saith God, I will pour out of my Spirit upon all flesh: and your sons and your daughters shall prophesy, and your young men shall see visions, and your old men shall dream dreams:
     "And on my servants and on my handmaidens I will pour out in those days of my Spirit." (Acts 2:17-18)

        On the day of Pentecost the Holy Spirit was poured out upon the disciples, and the manifestations of the Spirit "sat upon each one of them."

        When Peter preached the word to the household of Cornelius the Holy Spirit "fell upon all those who were hearing the word" (Acts 10:44).

     "And they of the circumcision which believed were astonished, as many as came with Peter, because that on the Gentiles also was poured out the gift of the Holy Ghost." (Acts 10:45)

        Significantly, Peter identified what happened to the household of Cornelius as the same thing that happened at Pentecost.

    "And as I began to speak, the Holy Spirit fell upon them even as upon us at the beginning" (Acts 11:14)

        Peter then reaffirmed the Lord's word establishing John's water baptism with the baptism with [the] Holy Spirit.

     "Then remembered I the word of the Lord, how that he said, John indeed baptized with water; but ye shall be baptized with the Holy Ghost." (Acts 11:16)

        The word "to pour out" is ekcheo.

"...bottles break, and the wine runneth out." (Mat. 9:17)

"...the wine is spilled" (Mark 2:22)

"...poured out the changers' money" (John 2:15)

"I will pour out of my Spirit" (Acts 2:17)

"I will pour out in those days (Acts 2:18)

"he hath shed forth this" (Acts 2:33)

"blood of thy martyr Stephen was shed" (Acts 22:20)

"Their feet [are] swift to shed blood" (Rom. 3:15)

(See also Titus 3:6; Rev. 14:10; 16: 1, 2, 3, 4, 6, 8, 10, 12, 17)

        It is clear that the above word describes something that originated from a superior location and is applied in a downward direction.  The wine is not dipped, the changers' money is not dipped (it was poured out upon the floor), and neither is the Holy Spirit dipped, nor is the believer dipped, or immersed, into the Holy Spirit.  The Spirit was applied to the believer.  This strongly implies that during water baptism the water (a type of the Spirit) was applied to the person, not the person to the water.  Just as the Spirit was "poured out upon" the person, the water was poured out upon the repentant sinner.  The water (Spirit) was the active agent.  Despite the etymology of the word baptism from bapto (to dip), the new believer was never immersed or 'applied to' the water.

There is another, related word, ekkuuno, also having the meaning of pouring out upon something or someone.

"all [Judas'] bowels gushed out" (Acts 1:18)

"on the Gentiles also was poured out the gift of the Holy Ghost" (Acts 10:45)

(See also Mat. 23:35; 26:28; Mark 14:24; Luke 5:37; 11:50; 22:20; Rom. 5:5; Jude 11)

So we have John's baptism with water looking ahead to Christ's baptism with the Holy Spirit.  The "mode" of the baptism with the Holy Spirit is pouring out upon the person receiving this baptism.

Note:  During the Lord's ministry on earth, his disciples (but not the Lord Jesus Himself) also baptized with water:

     "When therefore the Lord knew how the Pharisees had heard that Jesus made and baptized more disciples than John,
     "(Though Jesus himself baptized not, but his disciples,)
     "He left Judaea, and departed again into Galilee." (John 4:1-3)

It is presumed, since there is no scriptural evidence to the contrary, that the baptism performed by the Lord's disciples was identical in mode and meaning to that of John the Baptist.

Water & blood sprinkled on the Leper for cleansing

As for the living bird, he shall take it, and the cedar wood, and the scarlet, and the hyssop, and shall dip them and the living bird in the blood of the bird that was killed over the running water:
7. And he shall sprinkle upon him that is to be cleansed from the leprosy seven times, and shall pronounce him clean, and shall let the living bird loose into the open field. (Lev.

Same with a house with leporsy (Lev 14:41

Levites sprinkled with water to cleanse them (Num. 8:6-7)

Whoever touched a dead body and did not get the water of separation sprinkled on them was cut off from Israel (Num. 19:13-20)

 So shall he sprinkle many nations; the kings shall shut their mouths at him: for that which had not been told them shall they see; and that which they had not heard shall they consider. (Isa. 52:15)

Sprinkle clean water upon Israel

 For I will take you from among the heathen, and gather you out of all countries, and will bring you into your own land.
25. Then will I sprinkle clean water upon you, and ye shall be clean: from all your filthiness, and from all your idols, will I cleanse you.
26. A new heart also will I give you, and a new spirit will I put within you: and I will take away the stony heart out of your flesh, and I will give you an heart of flesh.
27. And I will put my spirit within you, and cause you to walk in my statutes, and ye shall keep my judgments, and do them.
28. And ye shall dwell in the land that I gave to your fathers; and ye shall be My people, and I will be your God.
29. I will also save you from all your uncleannesses: and I will call for the corn, and will increase it, and lay no famine upon you.
30. And I will multiply the fruit of the tree, and the increase of the field, that ye shall receive no more reproach of famine among the heathen.
31. Then shall ye remember your own evil ways, and your doings that were not good, and shall lothe yourselves in your own sight for your iniquities and for your abominations.
32. Not for your sakes do I this, saith the Lord God, be it known unto you: be ashamed and confounded for your own ways, O house of Israel.
33. Thus saith the Lord God; In the day that I shall have cleansed you from all your iniquities I will also cause you to dwell in the cities, and the wastes shall be builded. (Ezek. 36:24-33)

Hebrews sprinkling with water, etc.

And having an high priest over the house of God;
22. Let us draw near with a true heart in full assurance of faith, having our hearts sprinkled from an evil conscience, and our bodies washed with pure water. (Heb 10:21-22)