Free diving depth as part of solo dive certification?

[Nemrod]

@Nemrod. Thanks for your thoughtful reply. I see from your post (and profile) that you are quite comfortable with your underwater skills and have a lot of experience. As you know (and I know having been diving 27 years) equipment is more sophisticated and the sport in general is safer now than in the early days of scuba. In my opinion, relying on antiquated diving techniques and technology is akin to disabling your antilock brakes, your air bags and removing your seatbelts from your car because this is how cars were back in the day. Certainly one can drive without these safety features a whole lifetime and never suffer adverse events. However most would agree that would be riskier than driving with the safety equipment.

As a physician with an interest in diving medicine, I can tell you unequivocally diving to a depth of 100 to 120 and using the surface as your redundant air supply is much riskier than carrying along a redundant air supply. Hopefully you will never face that situation. While YOU might make it to the surface from that depth and avoid drowning, your risk of decompression sickness and arterial air embolism are going to be much much higher than a slow controlled ascent on scuba. Boyle's law applies to all divers regardless of their confidence or past experience. I favor a more conservative risk adverse approach for myself than you have chosen. But as you say: "opinions don't gain much ground when the s--- hits the fan".

If you read my first post, I outlined the two approaches that are COMMONLY used for addressing redundancy for solo divers, I adhere primarily to Rule 2 unless my dive needs to go beyond those limits to which I adhere then to Rule 1.

You, and many other solo divers it seems, adhere to Rule 1 entirely, and that is fine, but then you need to equip yourself to comply with that circumstance and that is perfectly fine. This is why I then brought up what constitutes true redundancy in terms of equipment and of course the diver needs to know how to rig the equipment and deploy the equipment via their training. Perfectly good approach to solo diving.

A. Don't assume that just because I enjoy vintage equipment that I do not have state of the art equipment and training

B. You have state some opinions, including the one where in you used the word "unequivocally." If you can site your references for your statements then providing sufficiently deep, reviewed, statistics to prove what is or isn't more dangerous then they are facts, but you have not done so, so therefore remain opinions.

In your first post, you asked where the free diving based limit came from and if anybody had heard of it, I have given you the background and reasoning on the why of that concept. I never made any statement that Rule 1 or Rule 2 (as I put them) were superior to one or the another, only that I primarily adhere to Rule number 2 and many solo divers do in fact base their maximum solo working depth on their free diving or horizontal swim distance. There are in fact many solo divers who do not use redundant systems. We instead use simplified rigging, simple/robust equipment that is not failure prone and consider the surface our redundancy.

In terms of the ascent, again, you assume it would be a panicked, rushed affair, a CESA, again, I did not say that nor is that the idea. The idea, is to use the free diving skills to make a LEISURELY 60 FPM ascent to the surface. Again, let me reiterate, I said nothing about a blow and go and shoot to the surface :shocked2:. This is the entire point of Rule 2 establishing a depth limit based on the individuals (easy) free dive or horizontal swim capability. You are not understanding the concept.

I want to also say, there is another limiting rule, that is long held by most solo divers, stay out of deco. STAY OUT OF DECO. Deco is like the ceiling of a cave, it is a barrier between the diver and the surface. Decompression solo diving, like solo in caves, is something that some solo divers do, true, but the majority do not.

Obviously if you are pushing deco limits or are in deco, and solo without equipment based redundancy, and there is a problem, then, Houston, we got a really big problem .

Whether solo or buddy diving, the diver should have a plan for the dive, the equipment and skill set to match the dive and use the chosen equipment and then stick to the dive plan. Busting a deco limit is a big NO-NO and using that technology you mention, a dive computer (or two, or watch and tables for back up) and some attention to your profile should keep any diver, solo or not, out of deco, unless planned for.

OP, here is the book I mentioned:

Amazon.com: Solo Diving, 2nd Edition: The Art of Underwater Self-Sufficiency (9781881652281): Robert von Maier: Books

Uh, it is not an all encompassing read, there is plenty of room in it to find fault, some of the material, is out of date and perhaps a bit dry but if you are a solo diver or interested in solo then it is still worthwhile to read through. The more input you have, the better off you are, this book is just another bit of info.

Last summer, I think one of the most fun dives I have made in some time, off the Commercial Blvd Pier (I think) at WPB, I swam several miles off shore and returned, maximum depth I think was 35 feet. Because the dive was shallow, I did not have redundant systems, I did not have a spg, I did not use a computer, I did not use a BC, I did have a surface float, a steel 72, a single stage bullet proof double hose regulator custom built and tuned by me, a snorkel tube and a compass. I was in the water for over three hours. My biggest concern were boats, but, they would have been a concern no matter alone or not, tons of equipment or not. BTW, on my surface float, I had a DAN rescue kit and a dive flag and I did have a sausage on my person. I also carried my camera. It was a great dive, turtles, sharks, tons of fish, got some great photos, got tired on my swim in but no where at any point did I wish for doubles or a pony bottle or even a BC(D).

The plan was simple, swim out east, swim down and follow the ledge and suck the tank dry, swim back west to the beach.

Here is my equipment after the dive:

Here is the place, I swam straight out from the pier:

A cool fish pic I took:

And me on the way back in, wondering if I might ever get back cause I was tired and cold:

A quick solo dive off Sunset House over the wall:

But why solo when I got this nice wife buddy :

Have fun, enjoy, be as safe as you can be within reason.

N

 

[handben]

@Nemrod, I appreciate your perspective and experience. Although, I've been at it for a while and have logged quite a bit of time under the surface; I suspect you've logged more.

It sounds like a fun dive off West Palm Beach; thanks for sharing. I recall the early days when J valves were used rather than an SPG. The riskiest part of your dive was probably the surface swim. I wouldn't expect your typical drunk jet skier to have much situational awareness so to speak. My closest brush with death in the water was nearly being hit by a rental speed boat at high speed in Bonaire while snorkling with my son. It made me re-think snorkling in water deep enough for boats to travel at speed.

As to providing a reference regarding my assertion (unequivocally ) that no redundant gas supply (other than the surface) is riskier than carrying a redundant gas, I will refer to the most recent (2010) DAN Fatality Workshop Proceedings:

"Knowing the root causes of triggering events probably provides us with the best information for preventing accidents. In the more than 940 fatality statistics studied, DAN identified five significant root causes:

1. Some sort of pre-existing disease pathology in the diver
2. Poor buoyancy control
3. Rapid ascent or violent water movement
4. Gas-supply problems
5. Equipment problems

In many cases the numbers indicate that more than one root cause was present at the time of the incident. These root causes have been identified as leading to the triggering events in 346 cases. The most significant triggering events identified were air loss, entrapment or entanglement, gear issues (which could include operator error), rough water and buoyancy issues. Not surprisingly, the causes of death in most of these incidents were either asphyxia (to include drowning) or arterial gas embolisms (AGE).

Some of the data, however, are surprising, and these surprises lead us to questions that can positively impact the industry. For example, insufficient gas was the trigger in 63 percent of fatal AGE cases and in 32 percent of drowning cases. This finding leads us to question the response divers may have to this emergency and, most important, the methods they use to prevent the situation from occurring in the first place."

The bold and italics were placed by me for emphasis, the rest was quoted from the latest issue of Alert Diver Magazine. If you are a DAN member, you can download the presentations from that conference. There was one presentation: Common Factors in Diving Fatalities - that goes into all of the statistics behind the above assertions. It is interesting albeit morbid reading.

 

[Nemrod]

This is what I think , you should get a pony rig or doubles set, independent or with an isolation manifold, which ever fits within your universe and an instructor that agrees with you.

If the instructor will not certify you, oh well, find another. If it were me as the instructor, I would not certify you beyond your easy horizontal swim distance. Solo is on the edge of acceptability among most training abc agencies and I imagine there is a wide latitude among the instructors who teach solo as to methods, which are probably their methods and might differ significantly from person to person, area to area etc.

Your DAN statistics, nice try, no cigar, they are largely irrelevant since they are based upon a minimally trained/experienced diver population that is trained to and in agreement with your statement prior:

Maybe I am missing something here, but to me free diving abilities and scuba diving skills are very different.

In order for the statistics to be valid they would have to include a control population of scuba divers trained in free diving skills, at least minimally, and self rescue, which is what your instructor is trying to get across, perhaps.

Good luck with the course.

N

 

[MauiScubaSteve]

Your DAN statistics, nice try, no cigar, they are largely irrelevant since they are based upon a minimally trained/experienced diver population that is trained to and in agreement with your statement prior:

In order for the statistics to be valid they would have to include a control population of scuba divers trained in free diving skills, at least minimally, and self rescue, which is what your instructor is trying to get across, perhaps.

Also with regards to the DAN Statistics, the vast majority of those statistics were not solo divers, they were bad buddy divers.

If I use 75' as my easy free dive depth (been past 100' twice) then my 2x depth would be 150'. I have been beyond 130' solo without other than the surface redundancy twice. I did have a scooter on one of those dives.

The non scooter dive was a kayak dive at Molokini (4 miles off shore); less than 5 minutes into dive see gray reef sharks deep, swim down fast to take a few pic's, look at gauges when it "feels deep" (136', 2600 psi remaining in 100 cft), return quickly to 110' where the white tip reef sharks are resting, work my way up "riding computer" (never less than 4 minutes remaining NDL time), 60 minute total dive time.

I would do the same again.

 

[DaleC]

N, I am trying to understand your POV. Did you mean you would not certify someone to dive beyond 2X of their freedive depth, regardless whether a redundant air source was carried or not?

 

[handben]

This is what I think , you should get a pony rig or doubles set, independent or with an isolation manifold, which ever fits within your universe and an instructor that agrees with you.

If the instructor will not certify you, oh well, find another. If it were me as the instructor, I would not certify you beyond your easy horizontal swim distance. Solo is on the edge of acceptability among most training abc agencies and I imagine there is a wide latitude among the instructors who teach solo as to methods, which are probably their methods and might differ significantly from person to person, area to area etc.

Your DAN statistics, nice try, no cigar, they are largely irrelevant since they are based upon a minimally trained/experienced diver population that is trained to and in agreement with your statement prior:

In order for the statistics to be valid they would have to include a control population of scuba divers trained in free diving skills, at least minimally, and self rescue, which is what your instructor is trying to get across, perhaps.


Good luck with the course.

Thanks!

N

I have purchased a pony as my bail out bottle. It is small enough to put through checked baggage without much trouble. I haven't used it yet; but am hoping that it will pretty much hang there and never get used... Pretty much the same way I feel about my car seatbelt. I wouldn't mind proving my skills in a horizontal swim test. I'm pretty confident that I could swim further horizontally than I'd care to go depth-wise.

With regards to the data validity, if the only way to provide a "valid" study for you is to include a "control population of scuba divers trained in free diving skills..." then you will never get this data as this would necessitate a prospective study. In order to get this data, you would need to set up the following: Take 2 populations of divers, one experienced the other inexperienced to a depth of 120 feet place them in an out-of-air situation and measure the outcomes. I believe that you are right that the experienced divers would fare better than the unexperienced; however no institutional review board is going to allow you to conduct an experiment so likely to cause significant harm to the subjects. Hence the only data we will ever have regarding diving mortality and subsequent risk analysis will be retrospective.

I believe that there is a good bit of "valid" data available for analysis and that conclusions can be drawn and recommendations made that can reduce risk for experienced as well as inexperienced divers. I'd say if we are going to try to reduce our own risk, analyzing the causes of other divers deaths and learning from their mistakes is an appropriate method and avenue.

Also with regards to the DAN Statistics, the vast majority of those statistics were not solo divers, they were bad buddy divers.

Regarding mortality statistics, the DAN data set actually show diving to be a reasonably safe endeavor. The rate of death is only around 1 per 200,000 dives. About 1/2 of the deaths were in divers with less than 20 dives. 40 percent were in a period of buddy separation. And 14% were in declared "solo divers".

I suspect that less than 14% of all dives are "declared solo dives" (this is opinion, I can't back it up with data), so it is somewhat concerning to me that we as a group (solo divers that is) are over-represented in the mortality data. It is a good reason for me to want to try to investigate root causes, triggering events and finally disabling injuries. I want to mitigate that risk to the extent that I reasonably can and still enjoy the activity.

Thanks to all for the thoughtful responses. I certainly appreciate a good dialogue on this subject. Although the discussion has strayed somewhat from the original topic - I guess that is ok being the OP.

 

[handben]

Nemrod, your prodding me for data sent me on a quest. There is at least one study (albeit retrospective) looking at the risk of pulmonary barotrauma (the major cause of arterial gas embolism and a major cause of diving deaths) in Emergency Free Ascent training. Source: Aviation, Space, and Environmental Medicine, Volume 80, Number 4, April 2009 , pp. 371-375. The authors are Belgian and analyzed data from their chamber in Brussels. They conclude that the risk for pulmonary barotrauma in an ascent training dive is "500 to 1500" times higher than a non ascent training dive (ie regular dive). I suspect that this data is the best you will find addressing the question of risk for doing a emergency free ascent versus on scuba. Given the strength of this data, most Belgian training agencies quit teaching this skill and have had no subsequent events of pulmonary barotrauma in training.

 

[dumpsterDiver]

It is ridiculous for someone to demand quantitative, scientifically valid research on diving accidents to address this issue. Solo diving with no redundancy to twice your freediving depth is about as unscientific, arbitrary and irrelevant as any rule of thumb I have seen and certainly has no scientific or even practical basis.

Of course freediving skills will make you a better (scuba) diver, but some sort of blanket depth limitation relative to freedive ability is really silly.

Also, the idea that some scuba diver is going to go out into cold water and try to set a personal best depth record while freediving, in order to generate some metric to allow themselves to "safely" solo dive with no redundancy is especially ridiculous!

Freediving to maximum depth is VERY dangerous, much more so than solo scuba diving to just about any depth. Freediving to any depth should only be done under the supervsion of a qualified freediver who has been trained in freedive rescue.

 

[DaleC]

I would agree with that.
I also see setting the max solo depth to twice your freedive depth as being potentially dangerous as it puts a soloist on the edge of the safety margin should they have to do an ESA (don't know how controlled it would be). Using the 2X max depth rule could lead a diver to think they don't need to consider redundancy for that kind of profile.
I imagine a failure on the bottom of a breath at max depth (worst case scenario). Now you are aiming to match your freedive limit while swimming up a rig and risking a shallow water blackout.
From my perspective it is better to have a conservatively safe no redundancy limit (whatever that is for the individual) and then plan to use appropriate redundancy after that.

But then, I am more of a plodder than a cowboy.

 

[LeadTurn_SD]

....Freediving to maximum depth is VERY dangerous, much more so than solo scuba diving to just about any depth. Freediving to any depth should only be done under the supervsion of a qualified freediver who has been trained in freedive rescue.

Agreed.

It concerns me a little that an instructor would want the OP to perform a max depth freedive (in a cold quarry!!). If the OP is not already an experienced freediver, does not have proper weighting and breathing/dive technique, and does not have a "spotter" in case of shallow water blackout.... frankly it makes me concerned.

It is one thing to do this in warm water with good viz.... cold water with "iffy" viz is another matter.

Best wishes.