Why is it impossible while 5m or more below water to breathe through a hose connected to the surface air, but easy to breathe through a scuba?

Question

Why is it impossible while 5m or more below water to breathe through a hose connected to the surface air, but easy to breathe through a scuba?

In: 158

Answer 1

There’s a few sides to this.

You can still inhale through a tube at 5m deep, so technically you can breathe. The issue is when you breathe out, the ‘used’ air stays in the tube. Oxygen will run out.

If you breathe out outside the tube, air doesn’t come in easily enough (physics) to last.

There’s also water pressure. This gets worse the deeper you go. It’s like a weight on your chest, making it harder to expand your lungs. I’m not sure at what depth this becomes a big issue. Could be 5m, could be 2, could be 20.