I had a discussion with a Young Earth creationist last week on Facebook and I found the conversation to be as interesting as it was astonishing. Since this conversation, I have removed myself from the Facebook debate group, due in part to my strong political views and in order to preserve my faith in humanity.
During the discussion that has since been deleted, I pointed out to this creationist that Noah's flood could not have happened as described in the book of Genesis. The reason for this was that there was simply not enough water on the face of the Earth to do it - otherwise, we would still be underwater right now. You would need to more than double all the water on Earth to cover all the land on this planet over the tops of the mountains as the bible describes.
Now given that the earth is already covered in about 70% water there really wouldn't be anywhere to store all that water nor any explanation of where it came from. At this, my opponent then responded with the suggestion that there are underground caves full of water that the water was ejected from them and later drained back into them once the flood was over.
When I pointed out that given the thickness of the Eart's crust and the amount of water needed to be held in these underground chambers to make up for the shortfall there wouldn't be much practical room left to build the stable ground we stand on.
Then he switched gears and started trying to convince me that it doesn't matter because you can have a global flood with less water than you would need to cover the surface of the earth. He stated with full confidence and conviction, that a lake near my house had enough water in it to flood even though it isn't flooded right now so that proves there must be enough water in the oceans for a global flood.
So in conclusion a lake that is flooded has the same amount of water in it as it would if it wasn't flooded.
Just like a glass of water that is half-full has the same amount of water in it as it would if overflowing.
I ended the conversation at this point and left the debate group.
I really wish I was making this up.