I just can’t comprehend how there are still spaces where water does not enter even when submerged
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Take a cup, turn it upside down and submerge it in water. See how air gets trapped in the top of the cup? Same thing.
Air is a thing that exists. You might not be able to see it but you can feel it moving like with wind, or blowing with your mouth. Air can be compressed but it always takes up some space, even underwater. I’m sure you have seen bubbles before as an example of this.
When a container like a ship goes underwater the air tries to escape towards the surface as water pushes in under the force of gravity. But if there is no passage upwards air can become trapped underwater. That is how air pockets can be created in sinking ships.
Also modern ships are designed with watertight compartments exactly for this reason. People can survive and equipment can be protected by sealing these compartments for rescue and recovery later
Air is lighter than water but can’t permeate the hull of a ship so the “bubble” exerts pressure on the water forcing it down. It’s basically trapped between a rock and a hard place so to speak.
It isn’t a case of the water not being able to get in, but instead a case of the air not being able to get out, the air won’t flow down to the bubble up to the surface, so if there isn’t a hole to the top air will be trapped inside and that air pocket will keep the water out.
Air isn’t “emptiness” it takes up space. If you try to push air underwater, it will want to float up because it’s less dense than the water. However, if you put something in the way that keeps the air from floating up then it gets stuck under the water, its still something that takes up space though, so it pushes against the water thats trying to flow into the space that the air is sitting in until it pushes hard enough to stop the water from coming in at all. You can test this by taking a glass cup, turning it upside down, and pushing it underwater. The air in the cup can’t float up because the cup is in the way, so it stays inside the cup and pushes against the water that is trying to flow in and keeps the water out.
The air is already in the ship before it submerges. As water comes in underneath, it pushes on the air, shrinking its volume and raising its pressure. But if the space that the air is in is airtight, then the air won’t be able to escape: it has to stay where it is, because there is nowhere else for it to go. The pocket will shrink until its pressure is the same as the water pressure, but it cannot just vanish. In order to let the water into the rest of that space, you have to find some way to let the air out. If that doesn’t happen, the pocket will stay.
You ever go swimming with swim trunks on and your trunks catch air bubbles in them?
A balloon pops if you pump too much air into it.
Hope this helps you visualise air as a quantifiable and physical.
Take a glass and turn it upside down, lower it in to the bath, a sink or bowl and note the trapped air, it is the same mechanism.
Air is lighter than water so wants to go upwards (actually the water wants to go downwards and pushes the air up but the net effect is the same). the glass/ship stops it from doing that
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