There was enough water in the great deep to flood the Earth 1,200 km deep. 15 cubits was when the crew of the ark stopped taking soundings. Mount Everest formed 101 years AFTER Noah's flood during Peleg's tectonics.
How Deep was Noah’s Flood?
The Volume of the Great Deep
When Noah's flood took place all of the waters of the great deep burst forth and flooded the Earth. If we know the volume of water and the radius of the Earth at this time, then we may calculate how deep the water was.
The Pillars of the Earth and it’s Original Radius
There are some clues for us to be able to figure out the Earth's former size. This comes from the pillars of the Earth which are part of its internal structure.
The Volume of Earth’s Mantle
It's very useful to know the volume of material in the Earth's crust and mantle, but before we move on it's also worthwhile to note that the Earth's crust and mantle have several Biblical synonyms.
Present Day Earth
With a few pieces of information we can take what we know about the Earth today and deduce what the Earth was like in the past. This is the alternative to using Uniformitarianism to assume that things were the same in the past.
Uniformitarianism
People presume to disprove God by cobbling together some math based on Uniformitarianism ideals that were popularized by Charles Lyell, a contemporary of Charles Darwin.
Noah’s Math
Some folk think that they can use 19th Century Uniformitarianism to show that Noah's flood didn't happen. We hate to break it to you, but, this is the 21st Century.