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Multiple deaths diving off NC coast May 10, 2020?

Discussion in 'Accidents and Incidents' started by Steve_C, May 10, 2020.

  1. Angelo Farina

    Angelo Farina Marine Scientist

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    Do we know how much capacity their tanks were?
    To me it seems impossible to run out of air at such depth (35m). With my tank (15 liters, 232 bars) I hit the NDL limit much earlier than having the tank at half of its content.
    But of course if they were using too-small tanks, you can easily run out of air...

    Last point: this is a case where the "primary donate" method was used, with bad results. It should be taken into account in the recent discussions about "primary vs secondary" donate. I remain convinced that the idea of "primary donate" is suboptimal in a number of cases, and that a regulator designed to be donated should have a longer-than-normal hose and should be routed "the wrong way" for his owner.
    When I was working as DM and guide, I always added a completely independent reg (first and second stage) mounted on the left post of my twin-valve tank, with a long yellow hose routed on my left shoulder (the "wrong" one), designated to be donated to my customers. Being "wrong" for me means that it was "right" for them, so no risk that it comes into their mouth upside down.
    And yes, it happened to me to donate it to my customers several times, always without any problem.
     
  2. Colliam7

    Colliam7 Tech Instructor Staff Member ScubaBoard Supporter

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    Impossible? Hardly. If the divers were not monitoring their air supply, it is entirely possible they were not monitoring their NDL. They were also diving 30%, which would have given them longer NDLs. But, whether they had passed their NDL limit already is both unknown and probably inconsequential.

    As for their cylinders, I am not aware of specific information being available on their rigs. But, if you look at the cylinders used in NC coastal diving, the vast majority are AL80s (207 bar, 77.4 cf of gas). Even if they were diving HP100s, that is not a lot of gas if the majority of your time is spent at 100fsw, and you are exerting yourself by finning to get close enough to spear a fish.

    As an example, I will use a RMV / SAC of 0.7 cfm (which happens to be mine). If I am having a relaxed swim at 107 fsw, my consumption is now ~3 cfm. If I am exerting myself a bit, chasing fish, and my RMV/SAC is closer to 0.9 CFM, then I am using ~3.8 cfm, which would give me ~20 minutes of time.

    Earlier in the thread there was comment made, to the effect that their bubbles stopped appearing at the surface ~45 minutes into the dive. That suggests they may have been down for an extended period of time.

    We don't know if they started with full cylinders, or had a 'short' fill, etc. But, the point is not to speculate, rather to say that running out of air in this situation, IF they were not reasonably monitoring their air supply, is not necessarily surprising.
    It is your privilege to 'remain convinced' of whatever you have already chosen to be convinced of. There are a number of very competent, experienced recreational and technical divers who 'remain convinced' that primary donate is a very functional approach to air sharing and is, in fact, preferable to alternate air source donation. But, the issue of primary vs alternate donate is - based on the circumstances apparently evident in the video, as reported here - completely irrelevant to the events in this case. In temporal order, it appears that a) the divers' failure to monitor air supply was the primary failure, which led to b) development of an OOA situation, which was c) complicated by panic (e.g. the OOA diver spitting the reg out before another air source was available), which was then d) exacerbated by poor performance in the sharing of a regulator (failure to properly orient the second stage). Other factors, such as the failure to ditch weights, were also apparently involved.

    This is a particularly rare event, not because of the cause (interruption of the air supply) but because there is apparently actual video evidence available which depicts the chain of events - the 'cascade'.

    This tragedy can, should, and must serve as a lesson for all. I will certainly use it as a case study in my teaching going forward. It should not have occurred, and would not have, IF the divers had monitored their air supply. It is quite likely that they were distracted by their fishing.
     
  3. Angelo Farina

    Angelo Farina Marine Scientist

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    Of course these divers made a number of errors, and I agree that this case can be very useful to study for avoiding other divers can repeat them.
    Still I think that using more appropriate equipment, as my own 15-liters tank, this sequence of events had been impossible to be triggered.
    Here a tank almost identical to my one:
    Bombole-sub-20180524134122.jpg
    As you see, it has a double post and THE RESERVE valve on the left (my one has also the rod, of course, which here appears to having been removed).
    Had I forgot to watch my SPG, when there is apparently no more gas to breath, I had simply pulled the reserve rod and got back the remaining 50 bars, plenty enough for concluding the dive in safety.
    So definitely the accident was caused by improper behaviour of the divers, but using some safer equipment, incorporating some redundancy, could have saved their life, despite their reckless behaviour.
    As it appears that this kind of tank, which is common here in Italy, is not available in the US, the correct equipment I had employed could have been a standard AL80 (which I understand is just slightly more than 10 liters) plus a side-mounted pony tank carrying at least other 5 liters.
    Diving at 35m with just a single AL80 tank looks already as a planning error, in my view.

    Regarding the primary donate: I understand that this technique was developed and found to be optimal for a very specific user case: diving in caves, in narrow passages, where a very long hose is the only way of supplying air to the buddy, and in a team approach where all the divers are trained and equipped in the same way (and are high-level tech divers). I agree that this is the best way in these circumstances.
    But consider a more common case: recreational unexperienced divers, employing a primary with not-so-long hose, which of course is routed "correctly" for the owner, but comes out to be "wrong" (upside down) when given to the buddy. In such case, I think it is better to have a dedicated "buddy reg", on your wrong shoulder, with a longer hose than your primary, and ready to become correctly oriented when donated. This is NOT your alternate air source. On my cylinder I use a standard reg (primary plus AAS), both routed correctly for me. And, on the second post, I mount another separate reg, which is the one designated to be donated (and NOT to be used by me as an alternate air source).
    I used this config for 5 years, during which I made approximately 1000 dives working in resorts, and this additional reg "for buddies" revealed to be useful in a number of cases...
    You could object that I did use additional equipment for covering lack of instructions and training of my "buddies" (we used to call them "clients" or "customers", indeed): which is definitely true.
    But in a commercial resort, for a number of reasons, you must accept that in your group there are also some not perfectly experienced divers, and you must take actions for being sure to bring all of them safely back on boat...
     
  4. rlskill1

    rlskill1 Instructor, Scuba

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    A tragic outcome that should have been avoided. Failure to follow simple procedures taught in Scuba 101.
     
  5. Colliam7

    Colliam7 Tech Instructor Staff Member ScubaBoard Supporter

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    On the issue of redundancy, I will agree with you. If I am diving at 100 feet, I will have a redundant air supply. I think that carrying a pony bottle - 19cf minimum, and preferably a 30 or 40cf bottle - is the better way to go than a J valve, but that's a matter of personal preference. As a teaching scenario, I certainly believe that this case supports the argument for carrying a redundant air supply.

    The issue of what size primary gas supply is appropriate when diving to 30+ meters is worth discussion. As I mentioned, it is common along the NC coast to see AL80s used for such dives. My personal preference is an HP 100 or 120, simply to provide enough gas to make the dive worthwhile - I don't care to spend ~2 hours on the boat getting to the dive site, just to have only 15-20 minutes on the wreck / site because of limited gas supply

    From the commentary in the thread, it appears that these were reasonably experienced divers, and they were using the same rigs they had used before. I have to believe that they were distracted during the dive and lost track of their gas status. Would the outcome have been different with a larger primary cylinder? Possibly, possibly not - the same level of distraction may have been present. But, with a J valve, or redundant air supply, they would have had an immediate bailout option when the primary supply was exhausted.

    In the US you still see some older J valves, most commonly on older steel 72s. But, you can actually buy them for newer cylinders, such as AL80s. ( XS Scuba PVD Reserve J Valve - Dive Tank Valves - Scubatoys.com. ) The discouraging factor is the price of the valve itself. For the cost of just the valve, you can essentially buy a small pony bottle, and a simple unsealed regulator first stage with a single 2nd stage.
    YES, that is the very sad and sobering 'bottom line'. I think it should also be a stimulus for us, as Instructors, to re-double our efforts - to reinforce the importance of basic procedures - e.g. planning dives and managing gas supply - and of continuing to practice basic skills (e.g. alternate air source use) after certification. There is a tendency for all of us, as divers, to review a case like this and conclude, 'I would never do something like those divers did.' And, that is a beguiling and dangerous conclusion.
     
    chillyinCanada and rlskill1 like this.
  6. Angelo Farina

    Angelo Farina Marine Scientist

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    I think that an AL80 is too small for a J-valve. After some calculations, my 15-liters tank translates to 123 CuFt. I would not use anything with lesser capacity for a dive down to 35m, in air.
    With Nitrox, which provides even longer bottom times, probably I had used my 3-liters pony tank in addition of my main tank.
    If only AL-80 are available, a pony tank is absolutely mandatory in my view, at least 45 or 50 Cuft.
    I hate to not have enough gas with me!
     
    Colliam7 likes this.
  7. johndiver999

    johndiver999 Solo Diver

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    Makes me wonder if a side exhaust regulator which has no "upside down" configuration might have prevented the aspiration of water and the vomiting and the dual fatality.
     
    Esprise Me and cathal like this.
  8. Colliam7

    Colliam7 Tech Instructor Staff Member ScubaBoard Supporter

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    Reasonable question. A couple of thoughts:

    Most regulators will breathe reasonably well when inverted. They will breathe 'wet', but they are still functional, IF the diver is not panicked. Irrespective of the discharge style, the mouthpiece orientation is probably a bigger issue. When the second stage is put in the mouth upside down, the mouthpiece often doesn't fit as well, and it is easier to ingest water.

    As much as I hate to speculate, I will offer the opinion that panic may have been an important factor, both in putting the second stage in upside down, and in the ingestion of sea water. I don't know that for fact. We will really never know.
     
  9. uncfnp

    uncfnp ScubaBoard Supporter ScubaBoard Supporter

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    I wonder too if she purged the second stage.
     
    Brilig and Esprise Me like this.
  10. Barnaby'sDad

    Barnaby'sDad ScubaBoard Supporter ScubaBoard Supporter

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    It’s not hard to blow through a good sized tank (ex. HP100 or HP120) if you’re fairly active during a dive at that depth. As they were hunting...I’m guessing their gas burn rate was higher than a typical dive at that depth.

    My two cents...at that depth and while hunting or fossil collecting (common off NC)...every buddy pair should have at a minimum one pony bottle. Sure...you don’t need it if “you plan your dive and dive your plan,” but if one person doesn’t, blows through their gas, panics, and has to go on their buddy’s gas while on bottom...you may end up with this unfortunate outcome.

    People are entirely too focused on NDL for dives of this depth and type. Depending on tank size and gas consumption...you’ve got a good chance of having to head to the surface before you hit your NDL. Ex. I never hit my NDL while diving there at ~105’. I had to surface each dive based on gas consumption.
     
    rjack321 and Angelo Farina like this.

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