"Known Unknowns...Unknown Unknowns" - Are they covered enough in diving?

[dumpsterDiver]

Is the U/K where most bad stuff actually happens? I.e. two divers ender a cave, untrained, they don't know the dangers. They kick up silt, get lost, die. Other people know to avoid kicking up silt and to use lines that they can follow out by feel, but the divers that died didn't know that.

If something is truly U/U, how can you even train for it? How do you train for what you don't know and nobody else knows either?

I'm not sure I completely understand all the terminology used in this thread, but my first inclination of how to deal with U/U is to develop the highest level of watermanship skills possible. For most recreational diving, a really serious problem is going to be resolved (or will kill somebody) in a pretty short time. You have a finite and often very short period of time to work on a resolution, and if you panic in that period, things may not go well.

So the very simple idea of: stop, think and act comes to mind. Ridiculously simple, but in reality, we often don't have a whole lot else to do. Maybe a rebreather diver has a long time to work out a solution, but in most serious diving situations, our critical time is short.

So the U/U might be addressed by stressing the diver out via various challenging drills, situations that require a degree of physical strength, calmness in a scary and stressful situation.. things along those lines which have been pretty much removed from recreational dive classes. The acquisition of a lot of time underwater probably helps a lot as well.

I suspect that a lot of serious problems are resolved or cascade into irrecoverable errors rather quickly - so your first reactions probably need to NOT be the wrong ones regardless of whether other people have had this happen or it is really an unusual or novel problem.

In the example above - with unqualified divers going into a cave. Been there done that.

Scared the living crap out of me. Ended up getting lost in a cave, separated from the buddy, not knowing which way to exist (even though I was in a straight tunnel with one way in and one way out). Everything went to hell in a few moments and I lost sight of the last bit of light streaming in from the end of the tunnel a few hundred feet away. Of course we had no lines or reel (since we were not even cavern divers).. i was just a PADI OW Instructor at the time.

An incredibly stupid situation to place myself in, but because I had just enough skill to know that the first thing a novice diver would do would be to kick up the bottom, I took a deep breath and floated up toward the ceiling - while I continued to totally freak out.. I had just the tiniest reserve of watermanship, knowledge and instinct to NOT do the wrong thing.

In the end, my buddy appeared (from her unplanned excursion into a recess), I did not kick up the water and she knew which way was out and we left the cave immediately - she had very little inkling of how terribly scared I was in those 30 seconds of terror. I could have easily kicked the hell out of the bottom and things could have gone badly.

On that particular day two divers (not qualified cave divers), died together lost in the cave while I was solo diving in another portion of the cavern probably 100 linear feet from them .. and this occurred maybe two hours after my little "lost" incident.

I ended my dive with the wife and 4 yr old son being told that daddy is dead, his body was located and we have to wait for the police divers to recover the two bodies. The wife was screaming and crying and beggin for the third buddy who found them to bring them to the surface and try to save them, but he just cried and refused and said it was too late.

The horror of the scene and the realization that I (and my GF) might have been a few fin kicks from the same fate, left a strong impression on me. Maybe that is relevant to this and the recent cave diving discussion.

 

[lermontov]

Well yes, but that wasn't really solved by the astronauts themselves...but rather by hundreds of engineers on the ground, who then radioed instructions to the crew on a fix. A diver doesn't have this benifit. Certainly you can train for the unexpected, but if it's too much, you're dead without external support.

and a lot less time

 

[DevonDiver]

Unknown / Unknown

My last U/U was when a tech student experienced simultaneous regulator failure - no gas delivered by either reg upon reaching depth. We'd done surface and descent checks, including s-drill with no issues.

Simultaneous failures of both regs aren't supposed to happen. A previously unknown issue caused this failure. (see my report: Nylon-Braided Regulator Hose Diving Emergency ) DAN are now writing a report on this risk.

Even though this incident was an U/U, good diving practices and ingrained protocols resolved the issue.

I was descending in close formation with the diver and this enabled me to notice his increasing discomfort. My hand was already on my long hose before he gave the OOG signal. He got air supply 1-2 seconds after. He gave the OOG signal because I was there...face-to-face at arm's length... and because we'd drilled gas sharing extensively and it was fresh in his mind.

Simultaneous failure of two regulators is supposed to be statistically near-impossible. Technical divers don't train for, or anticipate this scenario. Nonetheless, they do train to rapidly supply gas in response to an OOG signal.

That well-ingrained protocol led to an immediate cessation of the incident, even though the cause of the incident was not determined until later... when an autopsy was conducted on his regulator hoses after a complete strip and inspection of his 1st stages revealed no defects.

Known / Unknown

Another recent incident was a K/U. I was penetrating a wreck and a large (6' x 4' x 2") slab of plating fell on me. It was a relatively open area (boiler rooms) and the slab concerned was 3-4m above me. I assume it was just bubbles that finally caused it to break off and fall.

This is a known risk in wreck penetration, which is why I generally wear a helmet. Nonetheless, it's very rare (thankfully) for significant sized objects to dislodge and fall onto divers.

I was aware it could happen because over 25 years of wreck diving I'd heard first-hand accounts of it... and I'd experienced much smaller objects falling before.

However, there's no real adequate preparation possible for that eventuality.

It fell on my legs and was enormously heavy... but slow in falling. I just managed to drag my legs out from under it before it impacted on the top of a boiler. Quick instinctive reaction... as opposed to any sort of practiced drill. Nonetheless, quick reactions were probably possible only due to my awareness of the risk. I knew what was happening very quickly.

The plating would probably have snapped my lower legs... and possibly entrapped me.

My student at the time saw the plating fall on me. They heard the BOOM as it impacted and I disappeared in a massive cloud of silt. Afterwards, I was told that the thought in their mind when it happened was "OMG!.. my instructor just died"... and they were naturally very relieved when I emerged from the silt cloud some seconds later.

Known / Known

Another recent incident illustrates the K/K.

I was conducting a basic technical training dive (Tec45) and my student suffered a hypercapnia-related narcosis event - 'dark narc'.

I'm aware of this issue, have seen it before and knew the correct resolution.

I'd observed my student exerting himself more than optimally when kitting up, on entry, at the surface and on initial descent. Elevated respiration was observable, but not excessive.

Immediately on reaching the bottom of the descent, my student gave me a frantic 'thumbs up' to abort the dive. I complied immediately... experience telling me that zero delay or hesitation was acceptable.

My student later confirmed that they felt "extremely close" to panic at that point, but didn't know why. Any delay could easily have led to a full-blown panic reaction... very unsafe at 45m.

As we ascended, I noticed that his signs/symptoms were reducing. This confirmed my suspicion that he was suffering a gas-related issue triggered by raised partial pressure.

At 21m, I decided that the student was now capable of safely conducting a (closely supervised) gas switch onto 50%O2.

We hadn't incurred any deco obligation at this point, but I reasoned that the gas switch would eliminate any issues potentially arising from contaminated back gas (not ruled out at that point) and/or would help resolve any CO2 retention issues (my chief suspect was hypercapnia-induced narcosis).

As anticipated, switching to 50% rapidly resolved the issue and the remaining ascent was uneventful.

The event was textbook. My student was initially mortified and somewhat apologetic to have aborted the dive. He'd done deep recreational dives before (~40m) and never experienced any tangible narcosis symptoms. He was also a very psychologically robust person... and not used to feeling panicked or anxious.

Nonetheless, I'd seen this happen a few times and I understood the physiological factors that caused it. My message to him was entirely positive.

His decision to abort the dive demonstrated good stress management, effective use of procedures and laudable self-discipline. They admirably reflected the mindset and procedural systems that technical diving training strives to ingrain in trainees.

The incident was a K/K - it was easily and safely resolved through effective training that anticipates and mitigates precisely these scenarios