There is irrefutable evidence that proves the Sahara was once covered by the Ocean.
In fact, there is an area called "Valley of the Whale" because of all the whale bones and other ocean specie fossils that have been found there.
That’s true of much of the world, isn’t it? I can’t speak for the rest of the world, but here in NC, surface water drives groundwater out. Counterintuitive I know, but having been involved with putting a well in at a lake house, I can say that it’s a definite challenge and the well was unusually deep.