Baptism in the Koine Greek (the now dead language that the New Testament was written in) meant 'to dip repeatedly, to immerge,, submerge, (of vessels sunk, Polyb.1,51,6,8,4;) word #907 in Thayer's Greek-Englisk Lexicon of the new Testament.
It is a burial in water:
"Know ye not, that...