How to Drown a World

I did some nerding out on this once when I considered writing a Waterworld prequel fanfic for fun. Yes, I know how that sounds. This is the best I could come up with without turning Earth into a sterilized steam ball. The big constraint here is that we can’t simply smooth out the surface of the Earth because we know that Mount Everest still exists in the movie. There is enough water to cover the entire surface if land is smooth, but even if we went that route, it would be temporary unless we stop plate tectonics. And without plate tectonics, we have bigger problems.1

So the answer is to add water to the system. The pre-deluge civilization was advanced enough to mine and move material around the solar system. Asteroids, moons, maybe some of the dwarf planets. A project that large would mostly be automated. You cannot put enough people on every mining site, refinery, and cargo route to run it by hand and we know people don’t do well out in space for extended periods without some kind of artificial gravity.2

With all that going on, water would have been just one resource among many that they were gathering and processing. Since it is in space, the water would mostly be in the form of ice. The ice wasn’t meant to end up on Earth. To get to Waterworld sea levels, you need multiple oceans worth of water. That’s more than you could realistically get from the asteroid belt. So the ice would be coming from farther out, probably from icy moons like Europa, Ganymede and so on.3

Earth was the depot. Ice and other resources arrived close to Earth orbit, got processed and then was sent back out to wherever it was actually needed. Maybe Earth had the biggest processing facilities, the best orbital infrastructure or it was just centrally located for the civilization’s shipping routes.

The other important thing is that the ice cannot simply fall out of orbit. It doesn’t matter a whole lot whether it comes down as one large object or a lot of small ones. The orbital energy has to go somewhere. To deorbit enough ice to raise the oceans to the level of Waterworld would add enough energy to wipe out all life on Earth and vaporize enough water that we’d end up with a massive atmosphere.4

So the depot had equipment to catch incoming cargo, slow it down, and dump the heat back into space before doing anything with the resources. The resources could then be processed. With water, it would have to be purified to remove metals, other contaminants and all that, because if we don’t have that step then all the water that eventually ends up on Earth would be full of ammonia, methane, carbons and so on, which would create an unbreathable atmosphere. So once purified, the resources are stored in orbit, and then shipped out again.5

Then civilization collapses. A worldwide plague or something like that. Something that reduces civilization to a level where they no longer have the technology to manage the system.6

The mines are still running. The freight is still on its way. The depot is still able to receive and process it. But the shipping network is gone, and there is no one left to tell the system that it needs to stop accepting deliveries. Or maybe some of it keeps working for the non-water products.

At that point, the system has a problem. It can keep stacking up water in orbit until it becomes dangerous, or it can use its emergency overflow procedure and get rid of it safely. So it starts venting processed water into Earth’s atmosphere after it has already been slowed down.7

Nothing necessarily has to be broken. The system is doing what it was designed to do, following an emergency procedure that was never meant to run for centuries.8 It was supposed to be a temporary measure until human supervisors could fix the issue.9 So the rain keeps coming, sea levels keep rising and every generation loses more land than the one before it.

By the time of the movie, people might see the old orbital depot or the line of waiting cargo overhead, but have no idea what it is. It is just something the Ancients left in the sky.10

Eventually the system runs out of assigned mining targets, loses enough power or maintenance capability or starts missing enough incoming cargo that the backlog is depleted. Then the rain stops.11

The problem now is the timescale. This would take probably between 500 years to a couple thousand years. Too long for stuff like cigarettes, canned meat, oil and gasoline that the smokers used to have survived.12 And almost certainly too short to have the Mariner with his fully formed gills to have developed so quickly unless we assume that there was some pocket of technology left before the deluge who saw what was going to happen, and they were able to genetically engineer people that might be able to survive. It’s a stretch though.13

There are still other issues with this. For example, with the water levels in Waterworld, the ozone layer would be a lot thinner for close to a century after the flood stops, so surface radiation would be a lot worse. Most people would probably be blind by middle age, assuming they live that long. The high UV also means less phytoplankton, which is the base of the food chain, so there would be a lot less ocean life than we currently have. Luckily the ozone problem goes away fairly quickly, so maybe by the time of the movie, that’s resolved and is why people aren’t walking around with massive cataracts.14

Another big issue is that the worldwide ocean would be far less salty than current oceans but still not fresh water, which would be an extinction event. Anything that can’t move between fresh and salt water would likely die out.15 This almost works with the movie since the water is fairly empty of life. The giant water monster they show is probably not possible.16

Fast forward a million years and life will probably have started to adapt. Ten million years and the oceans might be full of life again. Plate tectonics is still a thing so we’d eventually see small volcanic islands but they would be rare.17

But given the world of the movie and what I’ve come up with so far, humanity is pretty much doomed. Even if the Mariner were not the only one of his kind, the odds of him and others like him being able to interbreed with the remaining humans to produce something that can live is pretty slim, though finding dry land at the end does improve their odds somewhat.18

That’s fair. Just spit balling but originally my concern with the fish monster was size. When the oceans first rise up and engulf the continents, we’d have a massive pulse of nutrients into the oceans and would see a temporary explosion of life. Eventually they will subside, probably within a century. So by the time the fish monster could have evolved, the boom would be over and there would be far less food available to it. But after thinking about it, I think it’s still believable that it would find enough food to sustain itself.19

The actual problem with the fish monster is complexity, not size. It is too radically different to have evolved in the time available. And if you extend the timeline far enough for it to evolve, you have extended it far enough that humans would be something else too and in the movie, it’s clear that the Mariner is either unique or rare. Most humans are still human, so it hasn’t been long enough. So one solution is that it did not evolve. It relocated.

The ocean gained roughly eight kilometers of depth, and two things followed. Pressure made the bottom uninhabitable. Everything that lived on the seafloor was crushed in place. The middle depths also are uninhabitable because a warm stratified ocean loses oxygen at depth.20 The ocean’s volume quadrupled and its habitable volume collapsed into a relatively thin layer at the surface.21

We could assume the monster was always down there. Nobody had ever seen it because nobody went that deep and we know that we are discovering new species in the depths regularly enough that this could be feasible. The monster is at the surface now because the surface is the only place left with oxygen in it. This would also suggest that it is not the only thing that came up, so as long as things coming from the deep are able to adapt to the reduced pressure, we could possibly have krakens as well.22