Could you survive at the deepest point of the ocean, if there was no water?

To answer this question we first need to know the deepest point in the oceans. The Mariana trench, measuring a depth of 10,910 m below sea level, is the deepest point, and at that depth there is a pressure of 1,068 bar, or around 1000 times the air pressure at sea level. Pretty heavy!

So, we want to know what the air pressure would be at that depth.

The pressure you feel when diving underwater is from the weight of the column of water sitting above you, so we can see that this pressure will be reduced if we remove the column of water and place a column of air there instead.

You can get an idea of how much air we are used to walking around under in day to day life. The definition of the end of the earth’s atmosphere and the beginning of space vary, but every day you have a column of air perhaps 100,000 m high resting on your shoulders, providing the atmospheric air pressure of 1 bar that we are all used to.

So what would the pressure be with an 110,910 m column of air instead? Around 3.66 bar, or 3.66 times atmospheric pressure, which shows just how much less water weighs than air.

So would a human be able to survive? Well, we have a convenient reference for this. 3.66 bar is the pressure at a depth of approximately 25m underwater, which is towards the deeper end of recreational scuba diving. There are some dangers associated with this, but that’s the topic of another question. It’s a little shallower than the depths at which the excessive pressure starts to cause problems, so you would probably be ok!