Does The Flood Add up?

It's curious how much effort is spent by creationists attempting to explain Noah's Ark as scientifically feasible when the story is one of Divine Intervention.If we make this, this, and this assumption -- if the Ark contained "kinds" instead of "species", if most animals hibernated and thus required no care, if migratory instinct brought them there, if the continental shelves and mountain chains were all squished down back then so the world's present water could cover all the land, etc. etc. --- why, it's possible!It seems that in coming up with a secular explanation, they're shooting themselves in the foot. After all, if the story is feasible without resorting to the supernatural, then one need not invoke the supernatural to explain it.

Here's one rather glaring example where a Biblical quote seems to contradict the assumption immediately preceding it.From http://www.carm.org/questions/noahsark.htm

Is there enough water to flood the entire earth? Absolutely! If the earth were perfectly spherical the oceans would cover all the land by more than a mile in depth. The biblical account is that it rained for 40 days and nights in which the floodgates of the heavens were opened up as well as the fountains from the earth (Gen. 7:11;8:2). There is a theory known as the canopy theory that states it had never rained on the earth up to the time of Noah and that a mist watered the plants (Gen. 2:6-6). The theory goes on to state that there may have been a heavy cloud or water vapor layer over the entire earth and that it was this canopy of water that became torrential rains during the flood period.

​

Did the flood cover all the earth? Yes it did. The depth of the flood waters is described in Gen. 7:19 as covering "all the high mountains under the entire heavens."

(text made bold by me)