Someone went through the process without without believing what is accomplished at water baptism.
No, it can't change what the water really is...the blood of Christ.Does "lack of faith" prevent the water from being the Blood?
Lack of faith will cancel what was supposed to happen. ie, the death, and burial of the old man, and resurrection with Christ of a new man.
It will cancel the circumcision of the flesh, and our insertion into Christ.
Nothing can change what God has ordained, only how it affects you.What about "false repentance"?
Let's look at the effects of a "real" baptism.Can you see why I think that in your theology, if a person sinned even once since they were water baptized, then it must not have been a real water baptism in that person's case?
Remission of past sins. (Acts 2:38, Rom 3:25)
Insertion into Christ, (wherein is no sin). (Rom 6:3)
Insertion into Christ's death and burial, and our partaking in the resurrection of Christ "to walk in newness of life"...rebirth. (Rom 6:4)
The circumcision of the flesh... (Col 2:11-13)
...with the affections and lusts. (Gal 5:24)
Freedom from sin. (Rom 6:7)
Any sin would betray the non-repentant as a man still in the flesh who was not reborn of God's seed. (1 John 3:8)
The baptism was real, but the baptized didn't benefit from it.