Seeing as you have touched on four different baptisms, for us to continue thinking there is in fact only one baptism is ludicrous.
It didn't seem to happen based on baptism (Acts 19:6 (KJV) And when Paul had laid [his] hands upon them, the Holy Ghost came on them; and they spake with tongues, and prophesied.), and it seems not to have happened every time. (1 Corinthians 12:30 (KJV)
Have all the gifts of healing? do all speak with tongues? do all interpret?)
If baptism is symbolized by water, but effected internally by the Holy Spirit, that's still just one baptism. Just like your reference to 1Cor 12, which is following up on what Paul talked about in ch 10--1 Corinthians 10:2-4 (KJV) 2 And were all baptized unto Moses in the cloud and in the sea; 3 And did all eat the same spiritual meat; 4 And did all drink the same spiritual drink: for they drank of that spiritual Rock that followed them: and that Rock was Christ.
If they were baptized unto Moses in the cloud and in the sea, it was still just one baptism--the sea was the water and the cloud was the presence of God's Spirit.
Paul's words saying there is only one must be considered in this way...There is one baptism administered by God, (and one baptism administered by men).