Today, while walking, I realized that there is not remotely enough water to have a Biblical flood to cover the world. Water does not just come and go. So I started thinking about how much of the Earth is rock and how much of it is water.

First, let's consider the total volume of rock and water on planet Earth: 

 Vrock = 1.083 (10)12 km3 : volume of the world's rock.

Vwater = 1.386 (10)9 km3: volume of the world's water.

The scientific notation hides a bit of the magnitude difference. Let's put the numbers side by side:

Vrock =  1,083,206,916,846 km3 

Vwater =        1,386,000,000 km3

Put another way, what percentage of the total Earth's volume is rock:

%Vrock = Vrock / (Vrock + Vwater)  = 99.9%  : the percentage of Earth that is rock

More importantly, if the Earth were a sphere of rock, then its radius would be given by:

Rrock = ((3 Vrock) / (4 π))1/3 

Rrock = 6.365 (10)3 km

 If we combine the Earth's water and the Earth's rock into a single sphere and compute the radius, we get:

R rock and water = (( 3 (Rrock + Vwater ) / (4  π)) 1/3

R rock and water = 6.368(10)3 km

If planet Earth were a perfectly smooth sphere, Noah's great flood would have blanketed it with 3 meters of water. But we know well that the Earth is not a sphere. Even the Bible mentions mountains. And if there were mountains, there would be ocean basins. Otherwise, where would Jonah's whale live? In fact, 97% of Earth's water makes up a home for Jonah's whale.

I've said it before: you need faith when you have no facts.

References: 

https://www.nature.com/scitable/blog/earthbound/water_water_everywhere/ 

https://oceanservice.noaa.gov/facts/wherewater.html