Why can't people breath underwater?
446486
Try SCUBA diving!!!!   I love swimming underwater too and love scuba diving.  It's the most incredible sport I've ever done.  You get to see all the great stuff in the ocean.  Try it!!!\n\nWhen you go through a certification course you can learn all about the human physiology and diving.  We have other differences from marine mammals that prevent us from diving like they do even if we could hold our breath longer.
1094383
Under what conditions?\n\nI recall seeing an article about a hotel in the Florida Keys that has made a series of underwater "bungaloes" that guests need to SCUBA dive down to, and out of.  Looks like it would be interesting.  And there are deep-sea researchers that live at depth for some time.\n\nBut either one requires a great deal of support at this time, since none of them could be considered self-sufficient.  Perhaps in the future?
188377
I *think* it's because they breathe through their skin - so when the soil and the underground fills up with rain water, they must come to the surface or drown. \n(I'm not 100% sure about this)
1006902
I think you mean gills.\n\nThere are artificial liquids available:\nLiquid breathing is a form of respiration in which a normally air-breathing organism breathes an oxygen rich liquid (usually from the perfluorocarbon family), rather than breathing air. It is used for medical treatment and could someday find use in deep diving and space travel. Liquid breathing is sometimes called "fluid breathing", but this is misleading as both liquids and gases are fluids.\n\nNanotechnology is be used to create respirocytes which act as artificial red blood cells and could allow you to hold your breath for 1-2 hours underwater.
799906
I don't see how sneezing underwater could be possible. I mean, getting the urge to sneeze occurs because something tickles our hair follicles inside our nose as we breathe. But because breathing underwater isn't possible without scuba gear, I don't think that getting the urge to sneeze underwater would be possible either.\n\nIf water did happen to get in your nose, your natural reaction is to immediately surface and breathe in air in order to clear your lungs. So if someone did somehow happen to get the urge to sneeze underwater, their reaction would be to surface and then sneeze.
745467
Dolphins do breathe air, but their skin/eyes/other stuff would dry out and eventually they would die
71077
Despite our ability to adapt to environmental conditions, there must certainly come a point where the surrounding pressure would overwhelm the solid portion of our structure--crush bones, break cellular walls, that sort of thing.  Deep sea divers can't go to the bottom of the deepest trenches.  I don't know whether they are crushed first, or some other gruesome death takes them first, but eventually I imagine whatever is left of them would be crushed.
985658
So living things can breath. Without air pressure we would not be able to breath.The air is thinner up in the atmosphere.Down here the air is Thicker and more dense then up there that's how we can live,with air pressure.With too much pressure or to little we could die.With too much pressure we could implode. Or too little pressure we could explode (I don't know how that would be possible but I think it's right) .That sounds funny that we would explode with too little
140188
I bet you could look this up on the web pretty easily. Why didn't you try?\n\nI bet the diffusivity is pretty good, however, because otherwise, how could fish breathe?
417041
Hi Steve, I had the same idea when I was about 8 years old and I can tell you from experience - it doesn't work!!  The increased pressure from the water pushing on your body makes it impossible to inhale from the hose.  Your lungs are designed to work at 1 atmosphere of pressure and they just are not efficient enough to suck in air like that while underwater.  It could also be very dangerous for someone who is not properly trained to breath off any air supply while submerged, if you were to hold your breath and ascend, your lungs would burst from the increased volume of air which would cause an injury called an Embolism - not a good thing!
894876
So they can breath. Their lungs aren't nearly as efficient as ours so they still require to breath through their skin, this can only be done on moist surfaces (this is also why our lungs are moist).
491213
Those 'oxygen enriched water' machines a scam. They are a way to take money off stupid people.\n\nNo, the human body can not absorb the oxygen present in water. Well, that's not quite true. You could absorb the oxygen in water if you breathed it in. Then you would drown. But if you are just drinking the water or bathing in it you can never absorb the oxygen in it.
320348
Deep ocean travel requires two things:\nProtection from the enormous pressure\nAdequate supply of oxygen and breathing gas for the safe return to the surface.\n\nAs we dive deeper, our bodies are subjected to the increasing water pressure.  This is especially so if we dive only to depths of less than 100 meters.  As we dive deeper, our bodies are subjected to greater pressure.  Our blood absorbs MORE gas (namely nitrogen gas); as we return to the surface, the increased amount of nitrogen gas in the bloodstream begins to leave the bloodstream.\n\nIf divers return to the surface too fast, the nitrogen gas will bubble out too fast causing a painful and possibly fatal condition called "The Bends".  So, divers must "acclimate" to sea level pressure slowly.\n\nDivers who dive very deep must remain inside pressure chambers in which the air pressure is slowly reduced to sea level pressure, gently allowing the (bloodstream's) absorbed nitrogen gas to escape safely.
479513
During pregnancy, there is a stage where the human fetus has gill slits, but by the time a baby is able to survive outside it's mother, these have disappeared.  Babies, as we would think of a baby, can NOT breathe underwater- they have air breathing lungs, just like you, and would drown.\n\nThere is something called the mammalian dive reflex, which slows respiration, and can allow someone to survive for a short time (perhaps a few minutes depending on the circumstances) under water just from the oxygen they receive from the water, however this works best in very cold water, which has more dissolved oxygen.  People with smaller bodies, like babies and young children are more likely to survive longer under water.  This is where stories of kids serviving under lakes for long periods (15 min, or so) come from.
162130
They live beneath the sea, so they definitely don't breathe.  I think that each individual cell in the Sea Cucumber absorbs oxygen directly from the seawater.
647325
self contained underwater breathing apparatus
311098
Not very much.  The water pressure on your body would prevent you from being able to bring in air that is at normal atmospheric pressure.  You need a compressor on the surface and a hose to breath from.