This is part two of a two part question. You can find part one here.(How to Cause a Hydrosphere Apocalypse Part I The Great Drought)
One of the more interesting movies I watched growing up was Waterworld. I never understood why no one ever talked about it, I always thought it was cool, the music, the action the endless ocean, what more could you want? Admittedly, as I grew up I understood that there wasn’t enough water frozen in the ice caps to make that future happen, only enough to put New York and a lot of other coastal places under 60 ft of water.
But what if there was a world where there was a planetary drowning?
So let’s imagine another interstellar expedition that has discovered a habitable water world. There are no icecaps at the poles, the water is clear and shallow, and there is an absolute abundance of marine life. But no dry land, not even a small set of islands.
But the more astronauts investigate this planet the more anomalies they come across. Dozens of species that come to the ocean surface to breath like whales or dolphins, several species that still have clearly defined arms and legs, and in the shallower parts of the global ocean there are clear trace fossils of foot prints as well as fossils of animals that clearly spent their entire lives on dry land.
The evidence is clear, this world was once not so different from earth until it experienced a Noah’s Ark level flood, only this time there was no dry land left to go to.
So where did all that water come from?
What scientifically feasible scenario could happen that would cause a life supporting planet to flood and loose most of its dry land?