The Bible teaches us that there is only one God (" Hear, O Israel: The LORD our God is one LORD" Deuteronomy 6:4). But God exists in three persons ("...baptizing them in the name of the Father, and of the Son, and of the Holy Ghost:" - Matthew 28:19 - notice that it is "name" and not "names", indicating that there is only one God). Jesus showed that He and the Father are only One God when He said "I and my Father are one" (John 10:30). They are related as follows: The Father sent The Son (John 3:16) and the Father and the Son sent the Spirit (John 14:26; 15:26).

1) Biblically, Jesus was not "buried" as in being covered over with earth below ground level. His body was laid in a sepulchre, which is a cave hewn out of rock above ground level with several chambers for placing dead bodies. Hence the body of Jesus was never underground. 

1 Corinthians 15:3,4 - "For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures; And that he was buried, and that he rose again the third day according to the scriptures." 

John 20:5-7 - "And he stooping down, and looking in, saw the linen clothes lying; yet went he not in. Then cometh Simon Peter following him, and went into the sepulchre, and seeth the linen clothes lie, And the napkin, that was about his head, not lying with the linen clothes, but wrapped together in a place by itself." 

2) The tomb in which Jesus was laid was like the tomb in which Lazarus was laid, from which he could walk out (not climb out) when the stone was removed from the entrance: 

John 11:38,43,44 - "Jesus therefore again groaning in himself cometh to the grave. It was a cave, and a stone lay upon it. ...And when he thus had spoken, he cried with a loud voice, Lazarus, come forth. And he that was dead came forth, bound hand and foot with graveclothes"

3) The word "thapto" that is translated as "bury" in Romans 6:4 ("Therefore we are buried with him by baptism into death") simply means to put into a grave, or to entomb, or to honour with funeral rites. e.g. 

Matthew 8:21,22 - "And another of his disciples said unto him, Lord, suffer me first to go and bury my father. But Jesus said unto him, Follow me; and let the dead bury their dead." 

Romans 6:4 can thus be translated: "Therefore we are ‘funeralised’ with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life." 

Hence there is no necessity for a person to be plunged underwater when he is baptised. Baptism is properly administered by sprinkling.

The Holy Spirit is God -- He is not a force (implied by the word ‘what’ you used) as no one can lie to a force ("But Peter said, Ananias, why hath Satan filled thine heart to lie to the Holy Ghost, and to keep back part of the price of the land? Whiles it remained, was it not thine own? and after it was sold, was it not in thine own power? why hast thou conceived this thing in thine heart? thou hast not lied unto men, but unto God." – Acts 5:3,4 - Notice that in the first part it is ‘lie to the Holy Ghost’ and in the last part it is ‘lie unto God.’)

Yes, Peter who denied Jesus 3 times was the same Peter who wrote some books of the Bible (ie. 1 Peter and 2 Peter). But unlike Judas, Peter repented of His sin (which was done out of fear for his own life, rather than out of malicious intent, as was the case for Judas’ betrayal) and was restored by Jesus Christ in John 21:15-27). All writers of the books of the Bible were in fact sinners who were mercifully forgiven and cleansed by God (e.g. Isaiah 6:5-7).