Buggered if I know, I still haven`t heard a decent explanation for it....
Oh and maybe humans were caught up in that bout of "hyperspeciation" after the flood, that sounds about ad hoc enough to make it into the YEC lexicon although as humans were involved it would have to become "hypervariation" (can't have humans speciating, it implys they evolve)....
most likely it would give off so much heat that it wouldn't be a flood as all the water would vapourize and turn the earth into the worlds largest pressure cooker.....