It's effective no matter what. (assuming that the community means what the words mean; we're not talking about Mormon baptisms here) HOWEVER, it's effective as a promise to be believed, not some magic thing that saves you without your knowledge. Basically, baptism says: "you're saved in Christ!" and I say: "oh good, what a relief! Thanks be to God!" but if I abandon God and become an atheist or something it won't help me. (it still counts though. If I come back, that was my one baptism, I don't need a new one.)