I was amused to see that someone else had though up my explanation for the waters over the sky. I developed that idea of ice crystals in space in a 2 second blinding flash of inspiration while I was trying to think of a response to someones objection on this thread.
Nobody has yet refuted the ice crystal idea, and I look forward to the objections.
In that creationist article rossum mentions they made the basic mistake of believing that mount everest existed in Noahs day and that the flood waters could not have covered all the mountains.
However if you imagine that in Noahs day earths geography was very different. Adam and Eve earlier lived in a land which was one single land, I think, Noah inherited this land. The seas were shallow and sub-tropical, the land was flatish with small mountains - because the land was one the mountain-building plate tectonics had not kicked in.
So there was no reason to have tall mountains.
If all the water currently on earth was placed on the surface of a perfectly smooth earth sized planet then the water would cover the entire surface of the planet to a depth of 7924 feet deep. If say, half the water had been in space above the planet; and if the seas had been shallow tropical seas, and if the mountains were 2000/3000 feet high; then when the water in space fell onto earth the whole amount of water on earth would then have covered every mountain on earth.
After the flood the water in the seas was deeper than the water on land, and so, was much heavier. The areas of water covering the seas beds therefore sank under the weight of water.
This broke up the sea bed and continental plates. The weight of water pushing down and outwards raised the land area above the surface once more and pushed the plates apart, creating features like the mid-atlantic ridge and volcanism on the plate boundaries. And where the moving plates met again and collided they raised the high mountains we see today - which incidently, (to add a note of realism), often have coral fossils from shallow warm seas in their rock.
The water on land simply drained into the seas and oceans as they grew ever deeper under the increasing weight of the waters.
Voila !