Already been done. It’s called SNUBA.
Google it.
I think it would me more like being squeezed between six ostriches and fourteen badgers.
Mangetout, welcome back! 
That just sounds wrong.
Since the OP has been answered, I’ve got to say that this device looks like a case of the bends waiting to happen. Hope your pump doesn’t quit while you’re down 90 feet.
I believe they were referring to something different, something portable…a underwater breathing apparatus that was self contained, as it were. Devil if if know what you’d call the device, though. Perhaps an “UBACS.”
There have been a few threads about this, most hilariously one involving a guy who attempted to retrieve his boat anchor by tying some free bench weights to his waist and jumping off the boat with a garden hose. Not a good idea. I’m not sure how deep this lake was supposed to be, but down at about thirty three feet, you’re at two atmospheres (2 ATM), and at 66 feet, 3 ATM. When you get to a certain depth, you’re not just worrying about not being able to expand your chest to suck air, you worrying about the air sucking you, or more specifically, your lungs. If you’re at several atmospheres of pressure and you have your mouth on a hose with one atmosphere of pressure, you’re basically sucking on a rather strong vacuum cleaner. Not a pleasant proposition.
It is, but no more so than diving with compressed air in a tank. (My old PADI tables go to 42 metres for an no-decompression dive with compressed air - 138 feet.) Pump reliability is of course an issue, and in the good old days people entrusted their lives to hand operated pumps and their operators. (Items 1231 and 2162, click through for more pictures.)
Mangetout, I’ve missed you! If it’s not too much of a hijack, I’m getting a 404 for your bird box webcam.
Meh, I think Marine Usage Freedive Freeair system is a better descriptor. . .
Back when I was a kid we visited Weekie Watchee – “The Spring of Live Mermaids” – down in Florida, and this looks very much like the system they used there. Basically a hose with a compressor at the other end.
Um, no. There is no vacuum effect as you describe. Having a hose in your mouth at depth is no different than merely opening your mouth underwater. If there were, every time you stuck a garden hose in a pool, you would have a geyser out the other end.
Thank you and thank you! - That’ll teach me to cut corners; I built the site using Netobjects Fusion instead of coding by hand, but when you change the heading text on a page, it changes the filename of the HTML.
Anyway, all fixed now… Cheers
I don’t think that’s right, because the tube in your mouth is empty, well, only full of air and leads all the way up to the surface; the water around you wants to rush up the tube and be level with the surface of the water way above you.
In fact, it’s a lot simpler; you are in a high pressure environment and you have an air-filled tube leading to a much lower-pressure environment in your mouth; flex727, you’re wrong, it would definitely suck.
Have you ever used a drinking straw? You draw liquid into your mouth by creating a pressure differential between your mouth and the ambient air pressure outside of the glass. Nature abhors your partial vacuum, and the high pressure of the ambient atmoshphere squirts a drink of tasty beverage into your low pressure mouth.
A little deeper, and water pressure does the work for you. Your pool probably isn’t sixty-six feet deep, but has enough pressure at the bottom to force water some distance up the hose. Let’s say you free dive down to the bottom of a very deep pool into which a two seventy foot pipes have been lowered, open to the air at the top and closed off with a watertight/airtight valve at the bottom. First, you exhale a bit into the water. Due to Boyle’s law, you still have as much air in your lungs as you did when you inhaled at the surface, but the volume of your lungs is decreased. The air in your lungs has been compressed to about one-third the volume it was at the surface. When you exhale ito the water, you’re inhaling into the same pressure that is pressurizing the air in your lungs in the first place. As the bubble rises, you can watch it slowly expand in volume, even though its mass has never changed.
Then you open the first pipe. Just like your drinking straw, the high pressure is going to equalize itself to the low pressure. Water may not shoot out the top like a geyser, but the water pressure is definitely going to cause the water to shoot up the pipe a distance.
Then you put your mouth on the secon pipe and open the valve. This time it’s not water shooting up the pipe and trying to equalize itself, it’s the compressed air from your lungs, and probably some of your blood vessels, too.
Grrr. Make that “When you exhale ito the water, you’re exhaling into the same pressure that is pressurizing the air in your lungs in the first place.”
Well, you and Mangetout are fairly persuasive and cause me to re-think my position. However, until I complete that process, I must say that I have actually performed this experiment when I was younger and even more ignorant than today. Perhaps I wasn’t deep enough, but when I tried to inhale through a garden hose from the bottom of my parents pool, no blood vessels or any other part of my lungs were sent to the surface.
Heh. A hookah system from a company called “Brownie’s”. Let me guess, if you come up too quickly, you’ll get a case of the munchies and have to recover in a cheech tank?
You were lucky, because the pressure wasn’t very high and lungs can actually compact down a lot without injury - apparently to the volume of a fist in the case of free divers.
But the problem of being connected to the surface by an inadequately pressurised tube can be very very nasty. Classically, it would happen happen to divers in the old brass helmet/tube to the surface days when something went wrong with the compressor or hose, leading to a loss of pressurisation, or if the air pressure was not increased rapidly enough when the diver descended. Then the diver would be subjected to massive water pressure trying to flow up his air hose and in the process squeezing him like a tube of toothpaste.
I had seen it mentioned in a book by one of Cousteau’s collaborators using its French name of ‘coup de ventouse’ - the english version is apparently ‘helmet squeeze’ or more formally barotrauma of descent
The account I read claimed that in severe cases they would pull up a smashed skeleton in a suit, with most of the soft tissue and fluids being in the lower part of the air hose. Probably an exaggeration - human bodies are pretty tough and don’t disintegrate easily.
I think that flex and slaphead are describing similar but very different conditions.
In flex’s experiment he is at the bottom of the pool, all parts of his body are exposed to the exact same pressure. he puts his mouth on a garden hose and tries to inhale. He did not mention what happened (other than no physical damage), but I am guessing that he did not get a lung full of air. This would be caused by: A) the pressure at the bottom of the pool, and B) the pressure of the pool probably squashed the hose flat. 
Now in sladhead’s example the depth is much greater than the 9’-10’ found in a home swimming pool. Let’s try a hundred feet or more. The pressure is enormous. If the pressure hose were to go to atmospheric the diver is suddenly exposed to the ambient pressure. This is bad, but not yet fatal. What kills the diver is the rigid helmet, it becomes like a vacuum chamber. Nature abhors a vacuum and tries to fill it. The only thing that can be pushed into this area of low pressure to get it to equalize is the nice soft diver. :eek:
If you have a pool, you could take a drinking glass, turn it upside down and place it just under the surface. The water will not flow into the glass due to the air pressure. Now dive to the bottom of the pool, and the water level will be higher inside the glass. Now picture how high the water level would be if the pressure were 5-10 times higher than the bottom of your pool. The air would be just a tiny bubble. Now picture your glass with a compressed air supply hose, some jello (molded to the shape of a man), and a plastic bag sealed to the bottom of the glass and surrounding the man. As you increase the pressure, you keep upping the air pressure so that the outside pressure and the inside pressure are equal. When you get to 100’ you suddenly dump the air pressure inside the glass/ bag to 1 atm from the 4 atm outside. Your jello man is going to be stuffed into that tiny air bubble in the top of the glass.
The difference between the two scenarios is the pressure and the presence of the helmet.
Yes. Ever try to siphom gas out of a tank?