The ONE baptism for the body of Christ is baptism INTO the body of Christ.... NO WATER.

1Co 12:12-13 KJV For as the body is one, and hath many members, and all the members of that one body, being many, are one body: so also is Christ. (13) For by one Spirit are we all baptized into one body, whether we be Jews or Gentiles, whether we be bond or free; and have been all made to drink into one Spirit.

THAT is the ONE baptism that Paul is talking about.