Within the context of those rules, there are a number of variations in emphases and strategies that can be expressed in the way the game is played, but the fundamental game is still the same. Christianity is much like that. There is a fundamental core of beliefs and teachings that identify any particular denomination as being Christian. That is why we call them Christian denominations. There are different points of view.
People have an idea about what is right and they follow that in their particular denomination.
Few would say that it really makes a critical difference whether you are dipped, sprinkled or immersed. Most would say that Christianity teaches baptism and that is something we all agree on. Even if you are baptized in a slightly different way, it doesn't mean the baptism doesn't count. Most of the differences in denominations are similar to this kind of thing. When it gets to mere Christianity, the basics and fundamentals are rather few.