There is some mention of a concept called "The fountains of the deep" in one of the two expositions of the flood story. Physical evidence that this concept ever existed (and you'd expect there to be some physical evidence of the source of a billion cubic miles of water, unless perhaps God erased the evidence in some kind of guilt-trip); zero, zilch, nada, zip.
I'd like to check alternative interpretations of the word translated as "fountains"
I'm convinced there was a real event and that it was more than the locals were accustomed to. Harks back to a Sumerian flood tale in many ways.