Stephen Baxter is a SciFi author who writes, in my mind, very gloomy novels (yet I keep buying his books).
A few years back he wrote a book called "Flood" (and its sequel "Ark").
The idea behind Flood was that sea levels started rising and most scientists put this down to global warming (ice cap melt and thermal expansion). One scientist demurred saying levels were rising too fast, she theorised there was a source of water under the oceans that was "leaking" and she was proven correct. There was no stopping it.
Eventually, in the novel, the water covered the entire Earth. Mass migrations, starvation, euthanasia centres, cannibalism - it's all in there (I said it was gloomy).
What reminded me of his book was confirmation that an enormous store of water has been confirmed beneath the Earth's crust. More water than is in all the surface oceans.
https://www.indy100.com/science-tech...ite-2659707032
Let's hope it doesn't leak.