I still have problems believing this: ‘Underground Oceans’ Potentially Have 3 Times More Water Than Surface - Study
It's the source of the "Fountains of the deep" from the Book of Genesis.
Earth doesn't have sufficient surface water (from rainfall and melting icecaps) to fully inundate the earth. To cover the highest mountaintops would require an additional 3 - 4 ocean's worth of water. It looks like they found it.
Only if pre-flood geography had mountain ranges the same height as post-flood.
Center for Scientific Creation
https://www.creationscience.com/
Better yet - here are the video explanations of hydroplate theory: