We woke up to find that the ocean starts to mystifyingly drain at warp speed, it drains in a speed that it will completely drain the ocean in a month(The mysterious draining only happens to the ocean, other water sources will not drain)


Survive to the utmost

Illustration of the earth with completely drained oceans

enter image description here

The Ocean is extremely crucial for living because it:

  • Holds a voluminous 321 million cubic miles (1.38 billion cubic kilometres) of water
  • Produces over half of the world's oxygen and absorbs 50 times more carbon dioxide than our atmosphere.
  • Regulates our climate and weather patterns.
  • Provides foods and ingredients
  • Is important for the water cycle.
  • Provides protein to nearly 3 billion humans and every plant, vegetable and animal has grown through access to water produced through the water cycle driven by the Ocean.
  • Controls Global Climate, Plays an important role in the Earth's climate and in global warming.
  • etc

Question: Given the amount of time before the ocean completely drains (1 month), what can we prepare to survive this as long as possible? (Using our current technology)

Water availability:

Citation from What-if:

If the ocean suddenly drained, the small amount of liquid left in lakes and rivers wouldn’t be enough to sustain the water cycle. The pools of drinkable water would evaporate pretty fast. In a matter of days, people and most animals would die from dehydration.

What can we do to preserve the rest of the waters and survive as long as possible?

One fact about earth's water: 2.5% of the earth's fresh water is not easily accessible, they are locked up in glaciers, polar ice caps, atmosphere, and soil. Some of them are highly polluted or lies too far under the earth's surface and will require loads of effort and money to extract.

More data about water distribution (excluding the ocean)

Water Source Volume (Cubic miles)
Ice caps, Glaciers, & Permanent Snow 5,773,000
Groundwater 5,614,000
Soil Moisture 3,959
Ground Ice 71,790
Lakes 42,320
Atmosphere 3,095
Swamp 2,752
Rivers 509
Biological Water 269

Oxygen availability:

50%-80% of the world's oxygen is produced by the ocean, well now its starting to disappear.... What can we do to preserve rest of the oxygen producers? How long can we survive with them?

What about the other factors? What can we do to preserve the rest of our alternative resources to stay alive?

Effect on gravity

The ocean accounts for 0.022 percent of the total weight of earth, weighing an estimated 1,450,000,000,000,000,000 short tons (1 short ton = 2,000lbs).

Oceans draining will cause the earth to lost this amount of mass which could also affect the gravity as gravity is a force and Force = Mass x Acceleration

Citation from Quora:

Scenario: Mass of earth is decreased by 10%

  1. Mass is reduced and the volume is also reduced. In this case I think the gravitational force of earth will also reduce will make everything on earth lighter. Average height of trees and may be animals will increase.

Now in this case, the ocean's mass is only a tiny bit portion of the total earth's mass(5.972 × 10^24)

Will the removal of this mass have any big effects on the earth's gravity or anything?

Extra question: If there is no way for us to survive this scenario, how much time do we have before everything completely dies?

  • $\begingroup$ "The ocean starts to mystifyingly [...] evaporate": nope, it cannot do that; the atmosphere cannot hold all the water of the ocean as vapor. Not even a significant fraction. Do something else with the water. $\endgroup$
    – AlexP
    Commented Aug 30, 2021 at 12:56
  • $\begingroup$ @AlexP yeah i changed "mystifyingly evaporate" to "mystifyingly drain". I'm not sure what else can i do with the water, any ideas? $\endgroup$ Commented Aug 30, 2021 at 12:57
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    $\begingroup$ I don't know how to crunch any numbers on it, but I feel pretty certain that the sudden (geologically speaking) removal of all that mass would trigger some NASTY tectonic misbehaviours. I would guess intense earthquakes at every coastline subduction zones. $\endgroup$
    – Qami
    Commented Aug 30, 2021 at 13:08
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    $\begingroup$ "other water sources will not drain" ...most other sources of water are continuously draining. Without oceans, rain will significantly decrease, and all bodies of water will start to dry out. Rivers will empty. Lakes will turn into muddy, stagnant pools. $\endgroup$
    – Matthew
    Commented Aug 30, 2021 at 14:52
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    $\begingroup$ Relevant XKCD. $\endgroup$
    – Mark
    Commented Aug 31, 2021 at 0:34

7 Answers 7


Biospheres (https://en.wikipedia.org/wiki/Biosphere_2) are probably our best hope.

Problems with temperature/pressure are insightful and real, but can be overcome with sufficient engineering. The big challenge is the change in water and oxygen levels.

Solution? Implement a closed-system water cycle of our own. Everything will need to be hermetically sealed, of course. Better draft all those scientists awaiting funds for their Martian bases, who will be overjoyed to help preserve humanity in this (comparatively forgiving) environment. You'll need a good balance of skill sets to rebuild civilization, but your plastic-wrapped arks and bases should be able to save a few people. Once the apocalypse ends and 99% of people are dead, it'll be trivial to go out in electric vehicles and scuba gear to forage for materials that could be used in base expansion. (Exercise left to the reader.)

Your only real challenge will be getting it all done and sealed in a month, with mass hysteria everywhere. But you only really need to get a few of these working initially, before expanding out. Hint: Start with the biggest mostly-sealed structures we have, ships. We won't have much use for them soon, anyways. Some even have nuclear power built-in.

Oxygen is conserved through hermetic seals, and recycled from carbon dioxide by plants (which also produce food). Gravity won't be much of an issue, as it will only decrease by the 0.022% you quoted. (Gravity and mass are directly proportional.)

Oh, and once things quiet down a bit, I'd recommend trying to extract and store up any groundwater you can in sealed containers for later. It probably won't be long before the water tables start dropping, without rain to replenish it.

And a final note - avoid coastlines and faultlines. The ground might be a bit shaky for a little bit here, as things settle.... (Cue landslide.) BUT, once things settle, maybe try the former seafloor for more forgiving ambient temperatures.

P.S. - Before you say it in the comments, YES, this would be extremely challenging. But, if this apocalypse came, it's our best bet to preserve humanity, in my opinion. We already have most of the tech. It's just not much time to implement it. At least we'd have motivation on our side.

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    $\begingroup$ Ships are not going to be a good place to be when there's no water to float them, because they won't sit horizontally with the keel underneath. Better to start with shopping malls and airport terminals. $\endgroup$
    – Graham
    Commented Aug 30, 2021 at 22:46
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    $\begingroup$ Good point. I think you could overcome that engineering challenge by settling the ship into a suitable trench or (better) a dry dock, or just building in it however it came to rest. Large buildings are a cool idea, even if they would be harder to hermetically seal. Airtight greenhouses could go on the roof in either scenario. $\endgroup$ Commented Aug 30, 2021 at 22:57
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    $\begingroup$ Large buildings will probably be a better idea as dry docking a ship will take a lot of planning, effort and time especially for big cruise ships that can accommodate 6000+ passengers. It will probably not be worth it as we only have a month in this scenario. I have no idea how long will hermetically sealing a large building take tho $\endgroup$ Commented Aug 31, 2021 at 2:43
  • $\begingroup$ Yeah, it would be hard with water levels dropping. But, there's bound to be a ready-to-launch ship in drydock somewhere. :) Again, you only need to survive with a few people at first to start repopulating the new Earth. $\endgroup$ Commented Aug 31, 2021 at 3:27
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    $\begingroup$ Don't the nuclear reactors on ships rely on the lots of water around them for cooling? The rest of the advantages may still hold (if you get it stabilized against tipping once the ocean below is gone), but I would go for one without a nuclear reactor. If those things can't generate power without an ocean below for cooling, the only thing they provide is dangerous materials. $\endgroup$
    – Syndic
    Commented Aug 31, 2021 at 5:17

The poor die

The rich die

The grass dies

The bacteria dies

everything dies.

For starters, the air pressure in current seaside cities will drop down to 30% of current levels. The same as if they were suddenly transported to 9000m altitude, just above the peak of mount Everest.
The oceans may only average 3.7km deep, but they cover a surface area 2.5 times as big as the land, and will take a lot of air to fill in to the current sealevel.

It would also become bitterly cold (due to altitude), and the air would be utterly dry.

So, every creature on dry land becomes a freeze-dried piece of jerky
In addition, every previously seagoing creature ends up at the very bottom of the ocean floor 12 km down, where it is exposed to some 1.5 bar of atmospheric pressure at about 50C, thus is created the universe's biggest Gumbo Stew.

So to repeat: EVERYTHING DIES, even bacteria.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – L.Dutch
    Commented Sep 2, 2021 at 2:48

Pump a lot of water out.

There are 50000 fire departments in the USA. There are probably a bunch of other pumps around the place. A fire engine can pump around 1000 gallons per minute.

Let's say the total pumping capacity of the USA is 1 million pumps in total, pumping a billion gallons per minute. Other machines like oil pumps and such would fill in any gaps.

That means in a day they can pump out about a trillion gallons of water. That's enough to run the USA for three days.

Radically reduce water usage and conserve existing supplies.

Water would become extremely expensive, and every possible method to recycle and maintain scarce water supplies would be needed. Existing water supplies like lakes and such would need to be covered to reduce water evaporation. Wars would start over large sources of water.

Low water crops would be grown to reduce water usage, and meat and other crops would be rare luxuries.

Plug the hole.

Desperate missions would be planned to try to stop the water leaking. Submarines, nukes, and all such things would get massive funding to stop the water leaking. If even a day out of the month of the water can be preserved, humanity can survive a lot better.

Even if they couldn't do that, if they could seal off a few trillion tons of water they could survive a lot better. People would do desperate things to try and preserve whatever bits of the sea they could.

Those who did preserve water would be the subject of fierce wars. Billions would die, as the scarce remnants of water ran out.

Fix the oceans.

There's a lot of comets and other sources of water out there. In the long run, we could get a bunch of them, and use them to restore the missing oceans, once we plugged the hole.

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    $\begingroup$ Pump water... where to? $\endgroup$
    – Alexander
    Commented Aug 30, 2021 at 17:25
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    $\begingroup$ To any containers they can find. $\endgroup$
    – Nepene Nep
    Commented Aug 30, 2021 at 18:10

Let’s try this.

The average person consumes 4 liters of water per day (https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/water/art-20044256) and there are 7 billion of us.

You can distill wastewater daily at a cost of about 2,250 kilojoules per liter, or 9,000 kilojoules per person, per day.


At a power price of 0.14 US cents per kilowatt hour, that will cost about 1,260 US dollars worth or power, per day, to recycle.

There are 7 billion of us on planet Earth, so you’d need at least seven billion 4-liter tanks, or an equivalent. 4 liters is 0.004 cubic meters. Let’s say they use the minimum amount of material as spherical tanks : 4/3 pi r^3, you need tanks about 0.1 meter in radius (0.2 meters in diameter), and maybe only a few millimeters thick. You’d need 0.125 square meters of sheet metal per tank. About 880 million square meters of sheet metal will be required to make seven billion such tanks. A single ton of steel produces about a thousand square meters of 3 millimeter sheet. According to this, 2017 World Production of sheet steel is about 200 million tons. So, if you direct production towards personal tanks for everyone you would only redirect about 1 million tons, or one half of one percent of the sheet steel production not including other metals and forms.


Filling these containers may be easy. 66% of the world has indoor plumbing. Reservoirs and ground water will not drain much faster than normal. So, even those without plumbing might notice something amiss and begin storing water.


Most growers rely on rivers or groundwater, rather than fickle rain, to grow. Depending on when this happens, at the beginning of the season when reservoirs are full, or the end of season when reservoirs should begin replenishing from rain, there could be as much as a year of business as usual, knowing this is the last such year.

According to this resource, the world has 1.2 million acres of greenhouse that will be able to hold onto humidity against the rapidly drying air.


One acre of crops can grow enough food for between 1 and 4 people, meaning somewhere between 1.2 and 4.8 million people have a food supply.

Good news, according to the same resource, about 13 million acres are “under cover”, which might be rapidly converted to greenhouse. Providing enough dryness-protected land to feed a total of 14.2 to 56.8 million people.

Some regions, like Central America with its freshwater cenotes may take much longer than a year to drain, and may be able to hold out with crops exposed to the dry air for several years.

According to this resource, an acre of crop needs 20 thousand to 40 thousand liters of water every three days. Or : between 2.4 and 4.8 million liters per year.

There is a LOT of groundwater trapped in the Earth’s crust. According to this resource, each cubic mile of water is 4.1 trillion liters.


Based on that, a single cubic mile of water could feed one million acres of farmland each year, feeding about 1 to 4 million people.

The amount of 5 million cubic miles of groundwater cited in the original question could, therefore, sustain 7 billion people for about 2,875 years (assuming all of the ground water could be exploited).

So, a major shift in how the world operates - and probably still a extinction level long-term problem; but not an insurmountable short-term problem.

  • $\begingroup$ the big problem is without oceans the air becomes super dry, so humans and plants actually loose a lot water just by respiring, today a human looses about a third of a liter each day this way, but in this super dry air expect losses higher than half a liter. the air will be dryer than any desert on earth. Another weird effect, all your farmland is now a too high an altitude to support crops. sea level now has air pressure closer to high mountains. $\endgroup$
    – John
    Commented Aug 31, 2021 at 1:54

Longer where it's winter

Anywhere where it's cold, you have large amounts of water lying around in the form of snow. In some places you may even have glaciers. These places are temporarily disconnected from the water cycle, so they're at a massive advantage. All available snow will be collected like it was gold dust.

Anywhere with lakes also has an advantage, of course. However the liquid water is going to be trying to flow to the sea and will also be evaporating, so a lot will be lost. Frozen water buys you more time to collect and store it


Most of the ocean doesn't drain.

As the water levels fall, the different oceans will become disconnected from each other and stop draining.

This is what the Earth will look like after the oceans stop draining:


(Image linked rather than directly included because of copyright.)

As a result, many of the apocalyptic predictions of all life on Earth (even the bacteria) going extinct are unlikely to occur. Instead, it's much more likely that, with shallower oceans and thin stretches of land where the mid-ocean ridges once were, there'd be a significant amount of livable space on the coast and the occasional super-continent with significant amounts of desert inland.

  • $\begingroup$ Ive read that article before, the ocean drains because there is some sort of portal opening up under the earth causing water to flow down which is why most of the oceans didnt drain. But in this scenario, the ocean will completely drain in a month, i didnt state the cause of the draining as its a mysterious event so this answer isnt really accurate IMO. I still appreciate the effort and points :D $\endgroup$ Commented Aug 31, 2021 at 8:28

The rich survive....oh and also those freaks obsessed with the apocalypse living in self sustaining bunkers.

Everything else dies.

How long can rich people survive the apocalypse? If they prepared for it with at least 2 or 3 years in advance, then they could survive indefinitively.

Some rich socialist/communist cities might thrive and survive like singapore, elsinki and beining.

Other countries don't have the politics to prepare or care for the survival of its population, but revolts might change that.

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    $\begingroup$ How can anyone survive indefinitely, whether rich or an allegedly socialist/communist city? Especially Singapore, which has major risks with its water supply already and relies on food imports? A fully sealed bunker with full atmosphere recycling can last as long as its power and supplies do, but that is not "indefinitely". No one has yet managed to make a long-term self-sustaining habitat, they certainly won't manage with one month's notice. $\endgroup$ Commented Aug 30, 2021 at 13:51
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    $\begingroup$ Singapore ... socialist or even communist? How strange. $\endgroup$
    – AlexP
    Commented Aug 30, 2021 at 14:25
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    $\begingroup$ "those freaks obsessed with the apocalypse living in self sustaining bunkers." couldn't survive 3 months of Covid self-quarantine before they started ransacking stores and generally going nuts. Not to mention complaining about needing a haircut, wanting to see a movie in the theaters, and basically everything else that was even a minor inconvenience to them. Those people survive barely longer than anyone not rich, and the rich are some of the worst that complained. Plus, you couldn't get them to keep their shelter secured, because they don't believe scientists telling them atmosphere is gone. $\endgroup$ Commented Aug 30, 2021 at 23:25

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