When I've encountered those who state that without water baptism we are not really saved, they have also stipulated that it must be a baptism by full immersion; no other means is said to be acceptable to God. They also have said that full immersion was necessary in order to truly cleanse us of our sins.
However, water cannot cleanse us of our sins, and never could. God demands that our sins be cleansed with blood:
First he said, "Sacrifices and offerings, burnt offerings and sin offerings you did not desire, nor were you pleased with them" (although the law required them to be made). Then he said, "Here I am, I have come to do your will." He sets aside the first to establish the second. And by that will, we have been made holy through the sacrifice of the body of Jesus Christ once for all.
Day after day every priest stands and performs his religious duties; again and again he offers the same sacrifices, which can never take away sins. But when this priest had offered for all time one sacrifice for sins, he sat down at the right hand of God. Since that time he waits for his enemies to be made his footstool, because by one sacrifice he has made perfect forever those who are being made holy. (Hebrews 10:8-14,NIV)
Through Jesus' sacrifice he made the perfect act of atonement. And those of us who accept as cleansing us of our sins the blood that was shed through that sacrifice have assurance of salvation, not because of our works, but because of God's own work through his Son:
Now we know that whatever the law says, it says to those who are under the law, so that every mouth may be silenced and the whole world held accountable to God. Therefore no one will be declared righteous in his sight by observing the law; rather, through the law we become conscious of sin.
But now a righteousness from God, apart from law, has been made known, to which the Law and the Prophets testify. This righteousness from God comes through faith in Jesus Christ to all who believe. There is no difference, for all have sinned and fall short of the glory of God, and are justified freely by his grace through the redemption that came by Christ Jesus. God presented him as a sacrifice of atonement, through faith in his blood. He did this to demonstrate his justice, because in his forbearance he had left the sins committed beforehand unpunished - he did it to demonstrate his justice at the present time, so as to be just and the one who justifies those who have faith in Jesus. (Romans 3:19-26,NIV)
Also, those who insist that only those who have been baptized by full immersion are saved have used the root word baptizo as evidence of their stand's being correct. This word has multiple meanings, depending on the circumstances which it is describing. But baptizo is also a greek word, not a jewish one. The person we call 'John the Baptist' was not called by that name until after Scripture was either written down or translated into greek. And Jesus would never have used that word in his conversations with his disciples.
Instead, he would have used the aramaic/hebrew word Mikvah. This word means to wash, but not to bury. In fact, archeologists digging in the holy land have uncovered mikvah pools, which were specifically used for this ceremonial washing. Without exception those pools have been so shallow that anyone getting into them would only have had water covering his ankles, rather than its being dep enough to drown in. The person would have stepped into the shallow pool, and then would have had water poured over him from a container. With the limited vocabulary of that day and age, the greek word baptizo was simply the closest to the aramaic/hebrew word mikvah, so the authors of New Testament Scripture used it.
