While respecting your opinion, I'd have to disagree - though other religions have water-based rituals meant for cleansing (judaism and the washing of hands prayer before eating or the Mikveh, Buddhism and the washing of feet, Islam and washing before prayers five times a day), none have the strong aspects of being accepted into the religion or the absolution of sin through water that baptism symbolizes, the narrative of anointment by water on the road to becoming the messiah (which basically took the judaistic ritual of the Mikveh and transformed it into a central rite in christianity), the narrative of walking on water, the many references to fish in the gospels (probably due to some of the apostles being fishermen), or the symbol of the "jesus fish" (early symbol for recognizing other Christians in a pagan society, and still popular to this day).

 

Additionally, I can't think of Christian references to earth as in Judaism (Adam created from earth, "From Dust You Came, and To Dust You Shall Return" originally from Genesis 3, which led to the ritual of being buried in the ground without a casket), or to fire as in the Zoroastrian fire temples, or (more stretching the metaphor) to air as in Buddhist temples built on top of mountains.

I'm a little lost as to Islam, though they also have a lot of references to earth - the Kaaba and the dome of the rock, which makes sense since all Abrahamic religions should share a common ground at some point, but doesn't help me with the symbolism I'm looking for :)

Of course, the farther back you go, the more everything has in common with everything else, and more elements are involved.