# Is it possible to breathe deep underwater with a pipe if enclosed in a box?

A problem in the physics textbook I was using asked how deep someone could go underwater and still manage to breath through a strong pipe or hose, assuming that the maximum pressure difference the person's lungs could handle was $-11.3$ kPa. The solution provided solved it by equating the water pressure at a certain dept to the air pressure in the person's lungs.

I was under the impression that since human body is made of muscle and bone, the water pressure wouldn't have much of an effect on the air pressure inside the lungs as the body would act like a rigid wall protecting the lungs. I was greatly mistaken because the pressure on the body underwater is too much for the respiratory muscles to handle and it is not strong enough to push back against the water pressure to expand the lungs(from this article).

If the body doesn't act like a rigid cage 'protecting' the lungs from water pressure, then what if there was a literal rigid cage filled with air at atmospheric pressure that confined someone as they descended underwater? Would the person be able to breathe through a pipe(strong enough to not collapse due to water pressure) that connected the cage to the air above water? Let's assume that the person only breathed in through the tube and not out, avoiding the problem of not inhaling fresh air.

• A submarine with a snorkel? Yes. – JMLCarter Mar 5 '17 at 6:07
• okay, well that was quick. I don't know what I should do with the question now... – E7_82_8E Mar 5 '17 at 6:14
• Doesn't mean it wasn't a good question. The pipe has to be strong enough too, I imagine that's the practical limitation on depth. – JMLCarter Mar 5 '17 at 6:19
• Submarine with snorkel is a good example, but really any compartment in a ship below the waterline would do. – Whit3rd Mar 5 '17 at 8:23
• The first submarine was a box with a snorkel, it was used by the americans against the english during the war of independence – veronika Mar 5 '17 at 10:45