St. Augustine - We enter the kingdom of heaven through Baptism

St. Augustine was a Catholic, not some strange form of quasi-crypto-proto-incipient-Protestant, notwithstanding the fever dreams of those Protestants who try to claim him for themselves. And as a Catholic, he understood that Baptism is the way that we gain entry to God’s kingdom.

And hereby, in Your Word, not the depth of the sea, but the earth parted from the bitterness of the waters, brings forth not the creeping and flying creature that has life, but the living soul itself. For now has it no longer need of baptism, as the heathen have, and as itself had when it was covered with the waters—for no other entrance is there into the kingdom of heaven, since You have appointed that this should be the entrance [Confessions XIII.21, emphasis added]

Now if this be the case, then it is clear that Baptism actually does something to us and for us, and if that is the case, then it is clear that the sacraments work ex opere operato, as the Catholic Church teaches, and as St. Augustine obviously believed himself.