Diving With An Unlimited Air Supply

If you want to explore underwater, you have a few options. You can hold your breath. You can try to recycle your air. You can carry your breathing air with you as in SCUBA. You can stick a tube up like a snorkel, or you can have air sent down to you from the surface. EXOlung falls into this last category, but unlike many other surface solutions, it has a twist: it never runs out of power before you do. Watch the video below and you’ll see how it works.

A buoy puts a snorkel up out of the water, and a tube lets you dive up to 5 meters away. There’s a small tank on your chest, and your body’s motion serves to fill the tank from the outside air supply. As your legs extend and retract, you fill the tank and then put the tank’s air at ambient pressure so you can breathe. As a bonus, by varying how you inhale and exhale, you can control your buoyancy and, therefore, your depth.

The system does require you to strap your legs up to the apparatus. However, other similar systems have compressors or batteries which can fail or run down, meaning there can be a limit on how long you can stay under. EXOlung claims there is no limit to how long you can stay under.

The cost looks to be around 300 Euro, although for a bit more you can get one that uses different materials to withstand higher pressures. That one has a 7-meter hose.

Another approach is to just carry a little air and remove the CO2 from it and rebreathe it. We’ve also seen a risky surface air pump that uses wind power.

82 thoughts on “Diving With An Unlimited Air Supply

    1. Indeed. I’m not a diver, but my first thought was to wonder what would happen if the diver became incapacitated in some way and could not provide the physical motion required to keep the air pumping. Seems pretty fail un-safe to me.

      1. I am a diver, and while this thing certainly isn’t without some risk, the scenarios people are suggesting are a bit overblown considering the actual operation of the system. Because the air supply relies on the user pumping it, to become incapacitated would require continuing to stay down after it was already clear the system was no longer working. Reaching the surface from 15 feet, even with empty lungs isn’t trivial, but it’s not too far from it for anyone of reasonable fitness.

        Some of the other issues people have suggested:

        Exhaustion: One doesn’t become exhausted all of the sudden and without warning. If a diver continues to stay down past the point exhaustion prevents them from operating the system, thereby compromising their air supply, that’s Darwin award material.

        Shallow water blackout. This happens at the end of breath hold dives when the diver is already hypoxic, and has trained his/her body to resist the urge to breath. It can happen when a diver just pushes themselves beyond their limit, or when the act of surfacing (and the drop in pressure that occurs) tips them over the edge. Divers using this should never approach hypoxia, and if they do, again, Darwin award.

        Buoyancy / turtling, etc. Did these people watch the video? It didn’t appear the diver was having any issues with either of these.

        Again, this thing is definitely not without any risk, but it’s also not a death trap for anyone with half a brain.

        1. I can think of one scenario: getting trapped in a discarded fishing net or line. A diver with a bottle has time to use their knife, but if you have to keep pumping your legs continuously you’re just getting yourself stuck worse.

          1. You assume that the diver in the bottle has an unlimited supply of air. Personally I would rather just pump my legs and take my time getting untangled than worry about running out of air with no recourse.

        2. Unexpected cramp from exertion is not unheard of diving. Most times it is an electrolyte imbalance but it happens even to inshape and long time divers. With a tank you have time to rub it out and leisurely return to the surface and signal for help. With this you arent pumping so you are using your tiny supply then no reserves.

          1. People are all about how dangerous this is. Come ON, look at it. You’re never more than 15′ below the surface, and all you have to do is relax and slowly let out that breath as you surface. Anybody who’s ever had SCUBA training knows this. You only get yourself into trouble when you get into a situation where you can’t find your way to the surface. And how are you going to do that, tethered to a 15′ hose?

        3. Again, it’s obviously not without any risk. One can think of all sorts of scenarios where a user of one of these could get into trouble, but the same could be imagined for real SCUBA gear. You could mis-analyze the mix of your Nitrox fill and end up with CNS convulsions. A faulty compressor could fill your tank with contaminated air. You could overstay your bottom time and end up with decompression sickness. Your weight belt could slip off causing you to panic and spit out your regulator (I saw exactly this in a class I was helping with. Never understood the spit-out-your-reg stress response). None of these things would happen on this device.

          If these were sold at Walmart, sure you’d have some people hurting themselves. But put that same person on a jet ski… and they’re going to hurt themselves. If you removed all the things an idiot could hurt themselves with, we’d all live in padded rooms lined with cotton wool.

          1. > If you removed all the things an idiot could hurt themselves with, we’d all live in padded rooms lined with cotton wool.

            … and some idiot would still manage to kill themselves with the cotton wool.

      2. Then it becomes a regular snorkel where you have to use your lungs to overcome the water pressure. In other words, when your legs aren’t doing the work to fill the air bladder, the device becomes just like what we have now.

        1. Except that water pressure on the diver will prevent it from working more that 12 to 24 inches below the surface. Just like a regular snorkel. If it stops working (or the diver stops working) then it’s time for the slow exhale emergency ascent procedure.

          1. Snorkels stop working very quickly at depth because the volume of the tube becomes a significant fraction of the volume of your lungs, and so trying to exhale through the tube you are simply re-breathing the same air.

          2. No, snorkels stop working below just a few inches, because it doesn’t take much depth for the pressure to be great enough that your diaphragm can’t exceed it. Legs are much stronger, but there’s no getting around the fact that you have to work harder, in proportion to the depth. So what’s going to happen, if you want to be below a few feet, is that you’re going to be getting cramps, or just plain wearing out. There’s no free lunch.

        2. You can’t pull air down to yourself due to the weight of the water pressure on the air. It feels like trying to pull a vacuum with your own lungs. Not possible. That’s why I don’t see this working out. The motion of your legs pulling three air down like a pump is interesting but I bet it gets tiring. If you stop, you’re dead.

          1. “you stop, you’re dead.” No, you’re not. You stop, you take one last breath, and you float up to that surface that is 15 feet above you. It’s true that there’s NO WAY you’re inhaling at 15′ depth – that’s about 7 psi, and it’s just not possible, but even if you can’t get that last kick in, one you rise a couple of FEET, you get more buoyant from the expansion of what air you do have in your lungs, to get to the surface. That would be the case even if you were at 100′ depth, which by the way this rig could never get you to.

  1. So, you keep breathing until something goes wrong and there’s no backup? For the price I think we’re going to see a lot of dead tourists… Solo umbilical means you just die alone.

  2. the whole thing seems interesting but one thing is total wrong: the movements of the legs. you move them like in freestyle and not like shown in the video. i asssume when you move your legs the right way the mechanic for storing and compressing air doesnt’t work anymore.

  3. The problem with this is that at 5 or 7 meters down the water pressure is quite a bit. I assume the numbers in the chart here are above the atmospheric pressure. https://www.engineeringtoolbox.com/hydrostatic-pressure-water-d_1632.html

    The legs of a person using this device are going to get tired rather quickly, pulling against the pressure on the diaphragm.

    Another issue is having this device on your chest will want to make you ‘turn turtle’ from the air buoyancy with every leg extension. Every time you kick out it’s going to try and push you towards the surface.

  4. Neat looking toy. Stupid though. In scuba, you dont typically bend your knees, you use your hips, and small movements to reduce heartrate and by process, air consumption. All the movements to make this work, are contrary to those used in the actual activity. And a random buoy acting as your lifeline and marker is downright irresponsible.

    A supplied air tube system has backups, is easy to service, and simple. Portable backup air canisters are easy to strap to the leg or chest. All of the currently used equipment has very high standards for safety and redundancy. Devices like this are akin to something I would expect to see hanging on the end cap at a wal mart for like, 10 dollars, which someone buys, plays with in their cousins pool for 10 minutes and breaks almost immediately.

    Things that try to simplify inherently dangerous activities for the purpose of circumventing tested and true equipment and training, and try to sell those same activities as something any random jackoff can do with some piece of crap- are plain and simple death traps. First and foremost, you never set it in someone’s head that it’s ok to dive alone because the gear is so simple.

    If you want to dive, learn to hold your breath. Dont want to hold your breath, then take the training and learn why the gear does what it does, and why you need a goddamn certification for it.

      1. “If something goes wrong..”
        That’s your fallback? Swim to the surface, get there out of breath, then get to try to get your breath back while treading water, since you’re not wearing a buoyancy device? If something goes wrong, you’re likely going to be swallowing water and having a nasty time overall.

    1. Your scuba experience is limiting your thinking. Scuba needs certain type of movement to conserve the limited air supply. This device needs certain type of movement to keep the unlimited air flowing. I think it’s just a matter of getting used to it and adjusting your way of thinking (and moving). You can still do your air conserving movements when you scuba…

      I’ve done a lot of scuba diving and find this very interesting. In my experience in tropical waters where there are coral reefs, most of the brightly colored fish you want to see are within about 5m of the surface. Snorkeling is nice but won’t give you much time to look at interesting things you find. Scuba tanks and buoyancy vests are bulky and difficult to move with (as well as difficult to transport to the dive site). To me this looks like a pretty good in-between device that will allow you to stay down longer without all the bulk, weight, and expense of scuba gear.

      I would love to try this thing.

      1. Like I said, its neat. I stand by saying it’s stupid.
        1. The pumps on the feet have added a brand new element of danger. You not only have a brand new risk of snags and tangles that you didnt have before, but the act of treading water to gain composure is hindered with the addition of additional resistance.
        2. Just getting air to a tube is easy, siphon systems are usually boat mounted and monitored. If a bigass wave takes out your buoy, you’re not going to notice until it’s in your mouth.
        3. Air conservation is not just about saving tanks- it’s about endurance aswell. If you’re burning energy just to keep breathing, you’re going to be breathing heavier, and keep amping it up until you’re spending more time pumping than swimming. Fins are made for mainly hip swimming, to use them primarily for otherwise is foolish.
        4. If something happens, and you have an air emergency, get tangled, attacked, injured…. you now need to worry about finding a way to pump this thing manually (if you’re conscious), before you get the joy of asphyxiation.
        5. One thing to see it in a pool. Let’s see a decent current.

        Knowledge is never limiting. If you wanna try it, fill your boots. I’ve built tons of crazy dangerous things that never should have been used, but I acknowledge their stupidity and lack of practicality from the get go.

        1. 1. can’t argue with the increased snag hazzard but having to tread water… you’re tethered to a floating bouyancy device. get hold of it, you only need to keep you head out the water.
          2. If you’re stupid enough to be using some thing like this in bigass waves it probably a mirical you made it this far in life (and that you didn’t suffocate your self while putting on your wetsuit)
          3. I’m far from my peak fitness but evevn i can maintain a 50 minute dive with continuous swimming and not come up exhausted. its not a race more a leisuely stroll round the park kind of exertion.
          while itss true you can move faster under water using a scissor kick, frog kick is more efficient and uses less energy if you not need to be moving quickly regardless of your fin type. though fin types can be designed to work more efficiently with different kicks, they all work for all styles.
          4.other than tangled if you have an air issue then go up. even at its 5m max depth you can pop up like a cork with no ill effects. risk not much more more than snorkling (I’m assuming most people still dive down while snorkling and don’t spend their entire time in the water floating on the surface like a dead fish)
          5.why would you be using this in a decent current? you wouldn’t normally be swimming or snorkling in those conditions so why would you suddenly want to use this device in them.

          Personally I’d take this over the spare air knock offs that are all over the chinese sites. at least with this there is a hard limit of 5m and you know if you stop kicking it will run dry. spare air just stops when thtere isn’t enough pressure for the reg to operate and you could be deeper than is comfortable to surface on a single breath.

    1. It looks to me like the “lung” strapped to your chest and the air in your own lungs serves the purpose of the buoyancy vest. I think it might take some practice, but easy enough to get used to it. You had to practice a bit to learn to use a buoyancy vest. This isn’t that different…

      1. A belt with several Kg of lead is needed. How much weight depends on your body type,and if you are using a wetsuit. Without a BCD you need the exact weight you need, you can’t inflate if you are heavy. No way to float at the surface and rest.
        I hope this device will never be sold. Last thing we need is clueless people damaging coral.

      1. The list of activities that would have to be banned as dangerous for “what if you passed out while doing it” would fill books. Soldering, using power tools, climbing ladders, riding bikes…

  5. The video is high on “wow factor” but very low on telling how this gadged actually works.
    What’s in that yellow bag? Is it one breath full of fresh air?

    I’m not into scuba, but I’ve read some stories about reef diving where the bubbles scared all the fish away.
    (I think this was about a re-breather which did not produce bubbles)
    Once you have a hose to the surface, it’s a small addition to add a 2nd hose to get rid of the bubbles.

  6. I wonder if they’ll one day create a diving backpack that directly electrolyses oxygen out of the surrounding water in sufficient volume for breathing in realtime – The energy requirements would be huge, but it’s a fun idea

        1. But the question is how does an animal adapted for the past 500 million years to absorb oxygen out of a gaseous oxygen/nitrogen environment absorb enough oxygen from water to keep it’s blood oxygen levels around 95+? Sure fish do it but were half a billion years out of practice.

          1. Since animal life began in the sea, the first transition was from breathing dissolved oxygen in water, to breathing the much easier to get at oxygen mixed in the air. And in the mean time there was probably a continuous chain of species that were amphibious.

    1. Is breathing air from a tube at the surface while you’re 15 feet down really that different from breathing air at the surface?
      Isn’t it really like breathing at the bottom of a 15 foot deep ditch on dry land?
      How does water pressure compress the air in a tube that is open at the top end?
      Fifteen feet is the diving well in the public pool I went to as a kid. It’s not that deep although I thought it was cooler than the 12 foot well at most other pools.

      1. The rule of thumb is one atmosphere (15 psi) for every 33 feet of depth, so roughly 1 PSI for every two feet of depth. And by the way, ONE psi is more than you can inhale.

        The pressure is caused by the weight of the water; every square inch of surface is supporting the weight of the whole water column above it. So no, it’s not at all like being 15 feet down in a ditch.j There, you’re only supporting 15 feet of air column.

      2. It would be just like breathing at the bottom of a 15 foot ditch if you had the weight of a 15′ column of water compressing your chest, that is to say impossible.

  7. For some odd reason this reminds me of a failed system I saw about 35 years ago, which used a sponge made with hemoglobin (ref: https://www.nytimes.com/1984/07/10/science/inventor-s-goal-artificial-gills-for-people.html and/or https://www.the-scientist.com/news/aquanautics-from-briny-dream-to-yeasty-reality-62552 ) to extract oxygen from water using a high flow rate of water and a pulsed high voltage source. After years of research into a workable solution they could never get around the need for a sponge the size of a football field and a prohibitively high amount of energy to force the hemoglobin to release it strong grip on the oxygen.

  8. I am very excited to try this product! I am a diver of 40 yrs experience and instructor.The video shows the device functioning with a very low level of exertion, so exhaustion does not seem a concern unless someone is in poor physical condition. An ascent from 15 ft is no problem for anyone with good swimming skills. I think the risk is similar to scuba; if a person does not have solid swimming skills they shouldnt be diving or using this device. It’s exciting to think about extended bottom time with no adverse effects since it it not compressed air!

    1. It literally IS compressed air though. If it wasn’t, you couldn’t pull it into your lungs.

      Also, it may LOOK like it is a low level of exertion, but do some math. How much force do you need to exceed the pressure at 5m depth? That is how much force your legs need to constantly output.

      1. To know the amount of work you have to expend, you must know how much air you need per unit time, which is a little circular, since the extra load increases the air requirement. But that can be worked out. We know that the pressure you have to work at is about 5 psi (sorry, I don’t even know what atmospheric pressure is in kpa, or what that translates to in N/cm^2), so all that’s lacking is the cubic feet (sorry again) of air per second necessary, to calculate the power requirement.

        According to https://health.howstuffworks.com/human-body/systems/respiratory/question98.htm, the average human needs about 7-8 liters/minute of air (not oxygen). But that’s at rest, and they just say “a lot more” for someone doing heavy exercise, without giving anything more to go on.

        https://www.ptdirect.com/training-design/anatomy-and-physiology/acute-respiratory-responses disagrees with them a bit, showing a rest ventilation rate of somewhere between 10 and 20 liters/min, and rates for light, medium, and heavy exercise at about 40, 80, and 120 liters/min respectively.

        Unless someone really wants the crunched numbers, I’m not going to work it all out right now. And in any case, I also don’t know how the ventilation rate varies with pressure, so there’s another unknown.

      2. Hi,
        Yes you are breathing compressed air. Its not an issue regarding deco sickness, but still a theoretical issue for lung barotrauma.
        Thats why you need to understand the basic physics behind, as a user.( no breath holding during ascent.)
        The math regarding exertion: The cross section of the current dive bell is approx.180cm2. That means a pressure of 90 kg in 5m =45 kg pull on your legs, since the pump bladder acts as a pulley, reducing the force to1/2.
        This results in 9kg pull per m depth.
        In my experience this isn’t really noticeable until approx. 3m , around 4 m the pull becomes apparent, still comfortable with a certain routine, 5m is definitely a bit sporty…I stay there for a few minutes max, until I return back to 3-4m usually. Beyond 5 m is possible, but its a sporty challenge, not relaxing for sure…and a lot of stress for the flex. bladder, leading to premature wear.
        If you feel the signs of overexertion, you wouldn’t return to the surface straight away… just slow down or stop the forward movement, which saves a lot of energy…if that is not enough you would just ascent e.g. 1m , to lower the pull and to recover. In case you feel completely out of balance / exhausted, you might return to the surface while exhaling ( matter of seconds, with proper fins) and hold on to the surface float.
        Exolung diving is basically all about energy management, you need to balance yourself out, in respect of breathing/ motion, but also in respect of trim and buoyancy control / body position in the water. Proper buoyancy technique and trim is the secret to save energy/oxygen = more relaxed and deeper diving. Like in every diving there is a strong mental component involved, even meditative. Thats why the Exolung can be seen as a recreational leisure device, but also as an exercising / yoga item, or just as a trivial utility tool for servicing your boat hull
        It definitely isn’t just an air supply. If you are looking for just that, you are probably better on with standard Scuba gear.


        1. Thank you for this. This is WAY more useful information than anything in the video. From what you’ve said here, I would be a lot more likely to try it. It does no good to pretend that there isn’t any exertion involved, since physics tells us otherwise. So the question then is, how MUCH exertion is it, which is a harder question, and I think you have answered it well.

          I wish you good fortune on your journey with this invention.

  9. Hi ,
    My name is Joerg, I am the inventor and developer of the Exolung. I am also the diver on all of the videos.
    I am following this discussion with interest.
    I’d gladly answer to all of your questions.
    (Please note, my English isn’t the best, I am Austrian…)


    1. Hey Joerg!

      I’m blown away by your invention!! This could be a serious step in diving. This is a great design. My colleagues and I find this very interesting. Absolutely amazing! I see a lot of potential for it on my diving and especially safety stops. I am very interested in buying when it comes out. My friends are too (btw, we are all diving instructors working in Maldives). All the best with design, test, marketing and innovating!


  10. Surface supplied air isn’t new. And it’s very limited…to say the least. If you want to stay underwater longer without the restrictions the current, only, and best way is diving on a Closed circuit rebreather.

    Case closed.

    1. No, the current one is super-weird. It uses chlorofluorocarbons liquid called Oxygent. You totally fill your lungs with it and play fish for a long time. It’s highly uncomfortable at first as you swear you are drowning. You just fill your helmet with a fresh supply and just breath that. It was in prototype phase decades ago. It was featured in a movie with Ed Harris. I forgot the movie name.

    2. Do you know of recent developments in rebreathers that make them less of a death trap than I’ve heard? Here’s what I remember:
      1) Because the gas is pure oxygen, you’re limited to about 30′ depth because below that you start getting oxygen toxicity.
      2) The chemicals used to scrub CO2 from the air can themselves give off toxic gases when they get WET, which seems like a bad thing.

      Furthermore, a rebreather doesn’t give you unlimited air; just more time underwater than a SCUBA system of the same weight. How much more? I don’t know, but it seems like it was 5x or maybe more than an air system. Again, pound for pound.

      And don’t forget, compressed air can be gotten for a pretty low price, especially if you have your own compressor. For a rebreathing ssytem, you need oxygen, and you need the CO2 scrubber media.

  11. Wow, this doesn’t sound like a hackaday crowd. Nobody is going to mention that this is amazingly simple device could be made from some 6″ pvc tube, waterproof fabric, 15′ of irrigation tubing and a snorkel?

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