Comprehensive list of all accidents

**UWSojourner** · 8th June 2008, 20:48

Quote: (Originally Posted by silent running)

As we don't know the full chain of events in most CCR accidents, all we can do is to speculate and then try to improve whatever can be improved in CCR design.

Besides speculation, we can read the accident descriptions. WOB isn't what pops into my mind in the overwhelming majority of the descriptions. Again, if we think WOB is problematic, we have to deal with why mCCRs are not entering the data proportionately.

I was just suggesting that if this is the place to discuss accidents, then move the "try to improve whatever can be improved in CCR design" to the CCR design forum. The alternative is to continue to enlarge this already huge thread that is supposed to be primarily discussing accidents.

heyydude · 8th June 2008, 21:28

You know, at the risk of seeming rather pedestrian to all the work-of-breathing experts the world over, I've got to say a couple of things...

1) Who, on this planet, knows more about human breathing underwater than the United States Navy?

2) Who, on this planet, has spent more money testing human breathing underwater than the United States Navy?

3) Who, on this planet, spends as much money on continuing research into human breathing underwater than the United States Navy?

4) Who, on this planet, spends as much money on purchasing and testing new underwater breathing apparatus of all makes and types than the United States Navy?

The answer: No One.

So - when the USN had a program to test and evaluate any and all rigs out there, which were winnowed down to:

a) Divex Stealth
b) Carleton Viper E
c) Mark 16 Mod 2

They eventually chose the Mark 16.

Now, you can argue that the Mark 16 breathes like a pig, or would fail CE, but in my mind (as a Mark 16 diver, as well as the creator of the Mod 2 and 3), it brings into question as to whether or not these extreme breathing requirements are truly "necessary" - meaning, in the overall scheme of things, how critically important can it be, if the US Navy doesn't deem it so?

I don't think there is anything wrong with trying to make a rebreather with great breathing dynamics - I just think too many people are thinking that these numbers that are bandied about are considered "minimum" safety numbers.

The truth is, I don't know anyone who has over-breathed a properly set up Mark 15/15.5/16. As a matter of fact, I don't know anyone who has over-breathed just about any rig out there, provided the scrubber was fresh...? ((If so, can someone enlighten me, please?))

When I was at ANSTI testing the Viper E and the Mark 16 Mod 2, we did some ridiculous tests (90 bpm, 1.6 lpm uptake) which no human I know could sustain (try it for yourself on the couch!) - so testing per-se is not the be-all and end-all of a discussion, or analysis of a particular rig.

Anyway - there are no doubt some who will denigrate the USN in this regard, but the truth is the truth - they possess the worlds leading experts on nearly every form of scuba diving (even if we civilians often think otherwise!), and judging by their continued use of the Mark 16 into the foreseeable future, that speaks volumes to me.

Besides, I LIKE my Mark 16...

And to ward off any tangents: The Viper E met all the same operational specifications/requirements as the Mark 16, so it wasn't for any particular Voodoo that is present in the Mark 16 - and believe me, I know ALL the Voodoo in that there rig, boy...

Kevin Juergensen
Juergensen Marine, Inc.

**DeepBlueInnovation** · 8th June 2008, 23:13

Hi Kevin,

As you say, no-one can match the resources of the USN, however military requirements often do not match civilian requirements. My understanding is that military operational requirements are for generally shallow diving, used by extremely fit individuals. Sports units are now designed to take divers to 100m, where there is a significant work of breathing difference to the 40m of USN testing, especially when you consider that most of the tech divers I have met do not exactly measure up to USN fitness levels...

Me included

In most situations WOB isn't an issue; but when the proverbial hits the fan it may be the difference between Davey Jones and a pint of Guinness.

I guess the best way to solve any debate on the matter is to put these units to the same civilian tests and see how they go - I genuinely don't know but am curious. Want to donate a new MK16 for testing

Cheers,

Ben.

***caveseeker7*** · 9th June 2008, 04:46

Isn't that akin of saying the Beretta 92 is the best, most reliable, most durable,
most accurate pistol because the US forces choose them as their sidearm?

I asume someone actually tested it before it was chosen ...

...
then again, since it was the choice, probably not.

Aside from politics and economics being very much part of the selection process.
Carleton Technologies is a billion dollar military juggernaut. What are the chances
of a a small company actually getting a contract from the US military?
Remember Biomarine? The contract went to Carleton. Even the HH upgrades now,
went to Carleton, correct? They're subcontracting to Juergensen Defense, aren't they?
Or Bantam ending up building trailers, while their little 4x4 design was build
by Willys and Ford ... ?

PCDiver · 9th June 2008, 05:06

Quote: (Originally Posted by heyydude)

As a matter of fact, I don't know anyone who has over-breathed just about any rig out there, provided the scrubber was fresh...? ((If so, can someone enlighten me, please?))

I did, two weeks ago in Indonesia. I was finning like a mad-man to get a good shot of a large school of mobulay rays with a big camera at 45 meters with air as diluent. The scrubber was fresh.

The air was becomming really hot. I've been in such situations before and I recognised the onset of severe breathing problems. I made the shot, I stopped, flushed, bailed out and took four sanity breaths. I went back on the loop and stayed calm. Problem sorted.

This was most likely not a case of the scrubber not being able to remove the CO2, but a case of CO2 retention.

Like we all know, a properly functioning well desigend rebreather has a higher WOB than a normal regulator. The higher WOB can easily cause CO2 retention during high exercise.

Instead of machine testing of the WOB of rebreathers, perhaps it would be better to focus on manned WOB rebreather tests.

silent running · 9th June 2008, 08:29

Quote: (Originally Posted by PCDiver)

Instead of machine testing of the WOB of rebreathers, perhaps it would be better to focus on manned WOB rebreather tests.

Hi PCD, wow, sorry to hear about your CO2 scare and I think you're right that manned testing is very important, maybe most important. And as such, it seems that nobody has done more manned testing of CCRs than the USN. I do much of my diving in conditions like you mention and USN standards have served me well so far... -Andy

SimonRichards · 9th June 2008, 15:39

Quote: (Originally Posted by AD_ward9)

...

Just on little point though, we go about testing WOB using the NEDU protocol with the EN14143 test depths etc. It defines WOB as the area enclosed by the Breathing resistance - volume Lissajou. I don't think the NEDU and CE definitions are right.

For example, take a Lissajou where the entire loop is positive pressure. Breathing in just involves opening one's mouth as the loop is positive pressure, but breathing out is harder. There is hardly any actual work in breathing in, but there is a pressure change from the mouthpiece to the suprasternal notch or lung centroid. That pressure change gets integrated and included as WOB. However, as it is positive pressure, all the pressure change is, is the effect of taking a gas volume out of the loop and putting it into the lungs.

Of course, going back the other way during the exhale cycle, the diver has to work against the pressure in the breathing loop to empty his lungs. The Work Of Breathing has nothing to do with the enclosed area of the Lissajou, but has everything to do with the integral of the exhale curve and the Y axis at 0mbar.

What I suggest we need is a better definition for WOB, which is the integral of the breathing resistance curve relative to the 0mbar axis, where negative values are treated as 0. That is real work of breathing. What everyone measures right now, has only a poor relationship with this real WOB figure.

Alex

Alex:

I don't think its a useful definition. It is thermodynamically meaningful if the energy transferred to the lungs can be stored and re-used on the exhale, but I suspect that is not the case. The same thinking suggests that there is zero net work in lifting a bag of concrete up and then putting it down again, but experience suggests that this is not the case either.

If one allows that the wear and tear on the human breathing system is more than linearly proportional to the pressure differential (which seems reasonable - I can breathe 24/7/365 against the WOB of my own airway), then a "RMS" integral would seem an intuitively reasonable measure of performance, and easy to deal with analytically. That would start penalising some rebreathers very heavily of course.

If you want a reductio ad absurdum demonstration of this, you could fairly easily build an O/C regulator with a negative WOB - you just need enough hysteresis in both the inhale and exhale valves. A steam engine is just a regulator with a very large negative WOB, of course (plus, literally, some bells and whistles). Such a thing could be made to be a pig to breathe from, but still outperform on the current WOB definition. Perhaps you should make a few of these and give them to the testers who stand by the current definition??

Regards,

Simon

AD_ward9 · 9th June 2008, 17:53

Quote: (Originally Posted by SimonRichards)

Alex:

I don't think its a useful definition. It is thermodynamically meaningful if the energy transferred to the lungs can be stored and re-used on the exhale, but I suspect that is not the case. The same thinking suggests that there is zero net work in lifting a bag of concrete up and then putting it down again, but experience suggests that this is not the case either.

If one allows that the wear and tear on the human breathing system is more than linearly proportional to the pressure differential (which seems reasonable - I can breathe 24/7/365 against the WOB of my own airway), then a "RMS" integral would seem an intuitively reasonable measure of performance, and easy to deal with analytically. That would start penalising some rebreathers very heavily of course.

If you want a reductio ad absurdum demonstration of this, you could fairly easily build an O/C regulator with a negative WOB - you just need enough hysteresis in both the inhale and exhale valves. A steam engine is just a regulator with a very large negative WOB, of course (plus, literally, some bells and whistles). Such a thing could be made to be a pig to breathe from, but still outperform on the current WOB definition. Perhaps you should make a few of these and give them to the testers who stand by the current definition??

Regards,

Simon

The reductio ad absurdum is the opposite of what I described: if there was a large negative WOB, it would be additive to the method I described, so would result in a high WOB figure.

We both agree: the lungs are not storing energy. When someone inhales or exhales against a pressure, energy is required to do that, which is not recovered. The present WOB definitions assume there is recovery. This is particularly the case with rebreathers due to the whole Lissajou being skewed by the movement of the counterlung centroid during the breathing cycle, and the fact that rebreathers can work with positive, or sometimes negative, pressure in the loop.

The WOB definition is an average breathing resistance, so it is taking the average rather than RMS. I also agree the RMS would be better, but the difference is fairly small. There is also an anomaly that sine flow rather than sine pressure drive is used in the current WOB definitions.

I will do a diagram just now to explain better, and post it.

Alex

Edit: added a 2 minute pic to illustrate.

AD_ward9 · 9th June 2008, 18:00

Quote: (Originally Posted by heyydude)

You know, at the risk of seeming rather pedestrian to all the work-of-breathing experts the world over, I've got to say a couple of things...

1) Who, on this planet, knows more about human breathing underwater than the United States Navy?
<snip>
I don't think there is anything wrong with trying to make a rebreather with great breathing dynamics - I just think too many people are thinking that these numbers that are bandied about are considered "minimum" safety numbers.

The US Navy do not know everything about human breathing underwater, otherwise they would stop doing research in this area. Moreover, all the knowledge in the world is not concentrated entirely in any one place, but spread amongst numerous labs working in this field as well as with divers. However, WOB is one thing that NEDU have been looking at a lot recently, with the result that they recommend the maximum WOB limits are reduced substantially. I understand this change is going into effect in STANAG 1410:2008, and it is being promoted by Qinetiq for a future revision of EN14143:2003.

See NEDU Technical Report TR 07-02.

Quote: (Originally Posted by UWSojourner)

While interesting, perhaps the WOB discussion also belongs elsewhere (maybe Rebreather design thread).
<snip>
Again, while truly interesting in the rebreather design thread, I'm not seeing the direct relevance of WOB to the accident thread until WOB is shown to be the cause of these accidents.

I agree it has expanded a lot so belongs somewhere else, but in safety rather than rebreather design at this stage. Mods must be busy chaps separating threads. On the proof issue, I quote ALARP (or HRDUBWD Principle in Post 554 of this thread).

Alex

Drmike · 10th June 2008, 03:01

Quote: (Originally Posted by PCDiver)

Like we all know, a properly functioning well desigend rebreather has a higher WOB than a normal regulator. The higher WOB can easily cause CO2 retention during high exercise.
.

Yes, if your exerting no matter if your using an Rebreather or oc if you breathe hard enough long enough you can start to suffer from reduced ventilation and retained co2. This will come faster when the wob is higher. Run down the road breathing through a straw. The smaller the straw diameter is the shorter the time to passing out will be.

Whilst chasing Ags bum along mainline Ginnie last year against a nice flow I had to stop after a while. I was having a retained CO2 hit with all teh assciated feeling as a hit from an exhausted scrubber. Even though boris has great wob I was finning like mad and simply over exerted

8th June 2008, 20:48	#591 (permalink)
UWSojourner Pacific Northwest Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Feb 2005 Location: Portland Oregon Posts: 556	Re: Comprehensive list of all accidents Quote: (Originally Posted by silent running) As we don't know the full chain of events in most CCR accidents, all we can do is to speculate and then try to improve whatever can be improved in CCR design. Besides speculation, we can read the accident descriptions. WOB isn't what pops into my mind in the overwhelming majority of the descriptions. Again, if we think WOB is problematic, we have to deal with why mCCRs are not entering the data proportionately. I was just suggesting that if this is the place to discuss accidents, then move the "try to improve whatever can be improved in CCR design" to the CCR design forum. The alternative is to continue to enlarge this already huge thread that is supposed to be primarily discussing accidents. Last edited by UWSojourner : 8th June 2008 at 20:55.
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8th June 2008, 21:28	#592 (permalink)
heyydude King of the Geeks Current Rebreather/s: MK 15.X Optima Other CCR Other Rebreather/s: Other CCR Join Date: May 2005 Location: Addison, Pennsylvania Posts: 357	Re: Comprehensive list of all accidents You know, at the risk of seeming rather pedestrian to all the work-of-breathing experts the world over, I've got to say a couple of things... 1) Who, on this planet, knows more about human breathing underwater than the United States Navy? 2) Who, on this planet, has spent more money testing human breathing underwater than the United States Navy? 3) Who, on this planet, spends as much money on continuing research into human breathing underwater than the United States Navy? 4) Who, on this planet, spends as much money on purchasing and testing new underwater breathing apparatus of all makes and types than the United States Navy? The answer: No One. So - when the USN had a program to test and evaluate any and all rigs out there, which were winnowed down to: a) Divex Stealth b) Carleton Viper E c) Mark 16 Mod 2 They eventually chose the Mark 16. Now, you can argue that the Mark 16 breathes like a pig, or would fail CE, but in my mind (as a Mark 16 diver, as well as the creator of the Mod 2 and 3), it brings into question as to whether or not these extreme breathing requirements are truly "necessary" - meaning, in the overall scheme of things, how critically important can it be, if the US Navy doesn't deem it so? I don't think there is anything wrong with trying to make a rebreather with great breathing dynamics - I just think too many people are thinking that these numbers that are bandied about are considered "minimum" safety numbers. The truth is, I don't know anyone who has over-breathed a properly set up Mark 15/15.5/16. As a matter of fact, I don't know anyone who has over-breathed just about any rig out there, provided the scrubber was fresh...? ((If so, can someone enlighten me, please?)) When I was at ANSTI testing the Viper E and the Mark 16 Mod 2, we did some ridiculous tests (90 bpm, 1.6 lpm uptake) which no human I know could sustain (try it for yourself on the couch!) - so testing per-se is not the be-all and end-all of a discussion, or analysis of a particular rig. Anyway - there are no doubt some who will denigrate the USN in this regard, but the truth is the truth - they possess the worlds leading experts on nearly every form of scuba diving (even if we civilians often think otherwise!), and judging by their continued use of the Mark 16 into the foreseeable future, that speaks volumes to me. Besides, I LIKE my Mark 16... And to ward off any tangents: The Viper E met all the same operational specifications/requirements as the Mark 16, so it wasn't for any particular Voodoo that is present in the Mark 16 - and believe me, I know ALL the Voodoo in that there rig, boy... Kevin Juergensen Juergensen Marine, Inc.
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8th June 2008, 23:13	#593 (permalink)
DeepBlueInnovation Learning to Kiss Current Rebreather/s: Not Bought Yet Other Rebreather/s: Prism Topaz Not Bought Yet Join Date: Sep 2005 Location: Perth, Western Australia Posts: 362	Re: Comprehensive list of all accidents Hi Kevin, As you say, no-one can match the resources of the USN, however military requirements often do not match civilian requirements. My understanding is that military operational requirements are for generally shallow diving, used by extremely fit individuals. Sports units are now designed to take divers to 100m, where there is a significant work of breathing difference to the 40m of USN testing, especially when you consider that most of the tech divers I have met do not exactly measure up to USN fitness levels... Me included In most situations WOB isn't an issue; but when the proverbial hits the fan it may be the difference between Davey Jones and a pint of Guinness. I guess the best way to solve any debate on the matter is to put these units to the same civilian tests and see how they go - I genuinely don't know but am curious. Want to donate a new MK16 for testing Cheers, Ben. Last edited by DeepBlueInnovation : 8th June 2008 at 23:16. Reason: To clarify my ignorance...
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9th June 2008, 04:46	#594 (permalink)
*caveseeker7* Who loves ya, baby Current Rebreather/s: Sport Kiss Other Rebreather/s: Prism Topaz Join Date: Jan 2005 Location: Too far from Neverland Posts: 5,498	Isn't that akin of saying the Beretta 92 is the best, most reliable, most durable, most accurate pistol because the US forces choose them as their sidearm? I asume someone actually tested it before it was chosen ... ... then again, since it was the choice, probably not. Aside from politics and economics being very much part of the selection process. Carleton Technologies is a billion dollar military juggernaut. What are the chances of a a small company actually getting a contract from the US military? Remember Biomarine? The contract went to Carleton. Even the HH upgrades now, went to Carleton, correct? They're subcontracting to Juergensen Defense, aren't they? Or Bantam ending up building trailers, while their little 4x4 design was build by Willys and Ford ... ? __________________ Cheers Stefan "Political Correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.!" Last edited by caveseeker7 : 9th June 2008 at 04:48.
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9th June 2008, 05:06	#595 (permalink)
PCDiver Submerge Productions Current Rebreather/s: Inspiration Vision Other Rebreather/s: Inspiration Classic Join Date: Feb 2005 Location: Belgium Posts: 964	Re: Comprehensive list of all accidents Quote: (Originally Posted by heyydude) As a matter of fact, I don't know anyone who has over-breathed just about any rig out there, provided the scrubber was fresh...? ((If so, can someone enlighten me, please?)) I did, two weeks ago in Indonesia. I was finning like a mad-man to get a good shot of a large school of mobulay rays with a big camera at 45 meters with air as diluent. The scrubber was fresh. The air was becomming really hot. I've been in such situations before and I recognised the onset of severe breathing problems. I made the shot, I stopped, flushed, bailed out and took four sanity breaths. I went back on the loop and stayed calm. Problem sorted. This was most likely not a case of the scrubber not being able to remove the CO2, but a case of CO2 retention. Like we all know, a properly functioning well desigend rebreather has a higher WOB than a normal regulator. The higher WOB can easily cause CO2 retention during high exercise. Instead of machine testing of the WOB of rebreathers, perhaps it would be better to focus on manned WOB rebreather tests. __________________ >>>>> www.submergeproductions.com dedicated to promoting technical diving >>>>> Check out our dive show video interviews and Wreck dive videos >>>>> Now also on iTunes and Zune
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9th June 2008, 08:29	#596 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,836	Re: Comprehensive list of all accidents Quote: (Originally Posted by PCDiver) Instead of machine testing of the WOB of rebreathers, perhaps it would be better to focus on manned WOB rebreather tests. Hi PCD, wow, sorry to hear about your CO2 scare and I think you're right that manned testing is very important, maybe most important. And as such, it seems that nobody has done more manned testing of CCRs than the USN. I do much of my diving in conditions like you mention and USN standards have served me well so far... -Andy
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9th June 2008, 15:39	#597 (permalink)
SimonRichards New Member Current Rebreather/s: Other SCR Other Rebreather/s: Other SCR Join Date: May 2006 Location: Mexico Posts: 3	Re: Comprehensive list of all accidents Quote: (Originally Posted by AD_ward9) ... Just on little point though, we go about testing WOB using the NEDU protocol with the EN14143 test depths etc. It defines WOB as the area enclosed by the Breathing resistance - volume Lissajou. I don't think the NEDU and CE definitions are right. For example, take a Lissajou where the entire loop is positive pressure. Breathing in just involves opening one's mouth as the loop is positive pressure, but breathing out is harder. There is hardly any actual work in breathing in, but there is a pressure change from the mouthpiece to the suprasternal notch or lung centroid. That pressure change gets integrated and included as WOB. However, as it is positive pressure, all the pressure change is, is the effect of taking a gas volume out of the loop and putting it into the lungs. Of course, going back the other way during the exhale cycle, the diver has to work against the pressure in the breathing loop to empty his lungs. The Work Of Breathing has nothing to do with the enclosed area of the Lissajou, but has everything to do with the integral of the exhale curve and the Y axis at 0mbar. What I suggest we need is a better definition for WOB, which is the integral of the breathing resistance curve relative to the 0mbar axis, where negative values are treated as 0. That is real work of breathing. What everyone measures right now, has only a poor relationship with this real WOB figure. Alex Alex: I don't think its a useful definition. It is thermodynamically meaningful if the energy transferred to the lungs can be stored and re-used on the exhale, but I suspect that is not the case. The same thinking suggests that there is zero net work in lifting a bag of concrete up and then putting it down again, but experience suggests that this is not the case either. If one allows that the wear and tear on the human breathing system is more than linearly proportional to the pressure differential (which seems reasonable - I can breathe 24/7/365 against the WOB of my own airway), then a "RMS" integral would seem an intuitively reasonable measure of performance, and easy to deal with analytically. That would start penalising some rebreathers very heavily of course. If you want a reductio ad absurdum demonstration of this, you could fairly easily build an O/C regulator with a negative WOB - you just need enough hysteresis in both the inhale and exhale valves. A steam engine is just a regulator with a very large negative WOB, of course (plus, literally, some bells and whistles). Such a thing could be made to be a pig to breathe from, but still outperform on the current WOB definition. Perhaps you should make a few of these and give them to the testers who stand by the current definition?? Regards, Simon
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9th June 2008, 18:00	#599 (permalink)
AD_ward9 So much more to learn Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Jun 2005 Location: Scotland Posts: 1,856	Re: Comprehensive list of all accidents Quote: (Originally Posted by heyydude) You know, at the risk of seeming rather pedestrian to all the work-of-breathing experts the world over, I've got to say a couple of things... 1) Who, on this planet, knows more about human breathing underwater than the United States Navy? <snip> I don't think there is anything wrong with trying to make a rebreather with great breathing dynamics - I just think too many people are thinking that these numbers that are bandied about are considered "minimum" safety numbers. The US Navy do not know everything about human breathing underwater, otherwise they would stop doing research in this area. Moreover, all the knowledge in the world is not concentrated entirely in any one place, but spread amongst numerous labs working in this field as well as with divers. However, WOB is one thing that NEDU have been looking at a lot recently, with the result that they recommend the maximum WOB limits are reduced substantially. I understand this change is going into effect in STANAG 1410:2008, and it is being promoted by Qinetiq for a future revision of EN14143:2003. See NEDU Technical Report TR 07-02. Quote: (Originally Posted by UWSojourner) While interesting, perhaps the WOB discussion also belongs elsewhere (maybe Rebreather design thread). <snip> Again, while truly interesting in the rebreather design thread, I'm not seeing the direct relevance of WOB to the accident thread until WOB is shown to be the cause of these accidents. I agree it has expanded a lot so belongs somewhere else, but in safety rather than rebreather design at this stage. Mods must be busy chaps separating threads. On the proof issue, I quote ALARP (or HRDUBWD Principle in Post 554 of this thread). Alex Last edited by AD_ward9 : 9th June 2008 at 18:49.
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10th June 2008, 03:01	#600 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,306	Re: Comprehensive list of all accidents Quote: (Originally Posted by PCDiver) Like we all know, a properly functioning well desigend rebreather has a higher WOB than a normal regulator. The higher WOB can easily cause CO2 retention during high exercise. . Yes, if your exerting no matter if your using an Rebreather or oc if you breathe hard enough long enough you can start to suffer from reduced ventilation and retained co2. This will come faster when the wob is higher. Run down the road breathing through a straw. The smaller the straw diameter is the shorter the time to passing out will be. Whilst chasing Ags bum along mainline Ginnie last year against a nice flow I had to stop after a while. I was having a retained CO2 hit with all teh assciated feeling as a hit from an exhausted scrubber. Even though boris has great wob I was finning like mad and simply over exerted __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment
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