You state: "Also the fact that there is no credible place for the water to have come from, there is no credible place it could have gone". That is incorrect. The Bible tells us a water canopy existed around the earth before the Flood. This harmonizes with scientific research that show the earth enjoyed a more temperate climate in the past. As to where the waters could have gone, the oceans are the obvious answer.
Let's start first with the water canopy idea.
This is, first off, bollocks. There is no credible mechanism by which water can maintain a 'shell' around the Earth without collapsing. Water does not float in shells around the Earth. Simple physics; it is impossible. Secondly, such a volume of water in the atmosphere would cause incredible atmospheric pressure.
This raises three points.
1) Greater pressure = greater heat. Noah et al. would have been living in the equivalent of a giant pressure cooker. 'Temperate climate' is a rather large understatement. The temperature would have been more than 25 degrees Centigrade higher.
2) When this canopy collapsed, the pressure would be released at great speed. Know what happens when a fish from the deep sea is brought up to the surface? It becomes depressurized and explodes. Noah and his animals, Ark or not, would have literally blown apart from the change in pressure.
3) When this canopy collapsed, the energy released would be greater than every single nuclear weapon on the planet being let off simultaneously, and then some, due to the massive conversion of GPE into KE. Noah and his guys would have been cooked.
Raising another point: in the 24th century BC, several civilizations, such as Ancient Egypt and the Indus Valley existed, and continued to exist, without any sign of extinction or damage from a global flood. Egypt has a continuous
written history going back to
3100 BC, (plus
archaeological evidence of continuous habitation going back to
9000 BC. Apparently they failed to notice their entire civilization being submerged by the Flood.