I think we make a mistake to think that baptism is a "symbolic" act, as if there were nothing really happening when one is baptized.
Too often we Christians tend to think "Is this what *saves* me? Because if it isn't what *saves* me, then it's just *symbolic* and therefore not really all that important."
Since Paul draws a direct parallel between baptism and circumcision lets look at circumcision again. Circumcision was an act of obedience. Did it *save*? No, we know that circumcision in of itself did not save, it was the faith of the circumcision that saved one. But, was circumcision just a *symbolic* act? Not at all. If one was not circumcised one was not part of the congregation of God's people. Period. The uncircumcised were not allowed in.
Now, I would imagine that, in the course of human events, there were a number of uncircumcised men, perhaps seeing God's miraculous interventions in the wars of His people that came to a realization that the God of the Hebrews was God indeed, and, in their hearts, bowed to Him in faith, and died on the battlefield. Would such a one be saved due to the faith, even though he wasn't circumcised? Certainly. But, had he lived, then he would have to be circumcised, he and all his male children and male servants, in order to truly be a child of God.
The point of circumcision was that it involved the shedding of blood. The Hebrews had a number of blood sacrifices that they had to make, and circumcision was the first of such sacrifices. Now, the blood shed during the bris and the blood of the animals that they brought for sacrifice did not save them. But, they wouldn't be saved without the shed blood either.
The waters of baptism do not save, but one (unless there are certain circumstances, such as the thief on the cross) will not be saved without baptism either.
Because, just as God worked in the shed blood of circumcision and sacrifices, God works in baptism. I was reading earlier responses to this thread and I must agree with francisdesales when he said, "it is God who makes Baptism efficacious, not the person's amount of faith or the type of water or the holiness of the minister. It is a work of God that is not dependent upon the individual."
This is the same belief about baptism that Presbyterians and Lutherans hold as well. The work of baptism for salvation is the work that God is doing during the washing. It doesn't hinge on a person's faith, or the type of water, or even the manner in which the water is administered.
If baptism was efficacious because of a person's faith, then faith itself becomes a work. Faith would then be something that we have to do, have to have "enough" of, in order to be saved.
But, we know that faith isn't from ourselves. Faith is entirely a gift of God.
And, just as God works to give us faith, He also is the One working within our baptism to wash us and cleanse us of our sin.
Baptism is not symbolic, God works mightily in our baptism.
Hebrews 10:19-23 states: "Therefore, brethren, since we have confidence to enter the holy place by the blood of Jesus, by a new and living way which He inaugurated for us through the veil, that is, His flesh, and since we have a great priest over the house of God, let us draw near with a sincere heart in full assurance of faith, having our hearts sprinkled clean from an evil conscience and our bodies washed with pure water. Let us hold fast the confession of our hope without wavering, for He who promised is faithful;"
We have assurance of faith (which does indeed come from God, not of ourselves) because of what Christ did on the cross (shed blood of sacrifice) and does in our baptism (cleanses our hearts from sin) and we can hold fast to this confession, again not because of our own faith, but because He is faithful.