As a rec diver, what to do if I breach my computer's NDL???

[CT-Rich]

This is what bugs me about SB, pile on, whether you're qualified to do so or not. I really appreciate the comments by qualified posters such as DevonDiver and TSandM, even if they don't fully appreciate the post.

Good diving, Craig

Up front, I am not certified for Deco. But if the people who you feel are qualified to comment don't appreciate you "flexible" view of dive planning and others that are not certified for deco are not qualified to comment on what you as an uncertified deco diver are doing, why are you posting?

If you are not going to accept criticism graciously, why are you asking for advise? Feel free to argue your point, but don't complain about others being contrary. The point of the back and forth in the forums is so that ideas get tested. If you are right, stick to your guns and articulate why you are right. Don't blame the culture of SB if you feel that people are piling on to you. Do you need to have a cert for deco? No law says so, but people around here have questions about your understanding of the risks involved in doing deco with out having a complete understanding of the risks involved in these dives. A ride in a deco chamber will put a big dent in your wallet and a complete recovery is not guaranteed and if you really screw the pooch you can die.

Do what you want on a dive, but if you don't like the responses on SB you have 3 choices. 1) you offer a clear, articulate explanation of your views that clarifies your views and persuades others, 2) You ignore the advise of others, rationalize your actions and continue doing what you feel is safe. 3) You look at the opinions of an array other divers and consider them and then re-evalutate your dive practices... Just don't complain about people who take the time to ask questions and offer opinions.

Dive Safe

 

[DevonDiver]

Here's how I see the thread:

OP: "I want to do X, Y and Z"

Others: "There are courses that specifically teach X, Y and Z"

OP: "I don't want to take those courses, they are not what I want"

Others: "WTF? Why not???"

OP: "Those are 'technical' courses, I want recreational"

Others: "X, Y and Z is beyond the parameters of recreational"

OP: "I want to re-define the parameters of recreational"

Others: "Why? When you have the training you need, available to you and accessible"

OP: "So I don't have to do those courses"

Others: bang heads against wall...

 

[TSandM]

It's all about risk acceptance.

Technical classes teach dive planning, in terms of being able to calculate how much gas you need for your dive and deco, and how much to have for contingencies. They also teach divers to be able to handle a variety of foreseeable issues, while remaining underwater and on schedule.

I am quite sure that the academic part of this can be learned by anyone with sufficient curiosity and a willingness to do practice problems. I'm also quite sure that a diver who understands the concept, can practice emergency procedures underwater until they are quite smooth. CMAS, as I understand it, DOES teach some decompression to their recreational level divers -- I have no idea what they teach for gas planning or redundancy, but they do teach it.

I have friends who do dives that incur deco on a single tank with a tank of deco gas. I wouldn't do that; I'm too risk-averse. They have looked back upon their own, extensive single tank experience and decided that, if they have done 4000 or so dives without a massive gas failure, it's unlikely to happen tomorrow (and they are probably right).

The line between recreational and technical diving is not a bright line. It's a gray area. People who have progressively expanded both their diving capacity and their knowledge can probably dance along the NDL line and do it safely. The problem is that most divers not only don't have the knowledge or the skills, they may not know what the knowledge IS that they need, or how to find it, and may have no conception of the skills. Most people would be better served with getting training. Some folks have mentors at hand, or just the plain old perseverance to learn what they need on their own.

 

[DevonDiver]

I'd go further. It's about risk acceptance versus risk mitigation.

There are a number of skill sets and protocols that can be added to a diver's repertoire in order to move from risk acceptance approach to a risk mitigation approach. Those skill sets and protocols increase in significance and effectiveness when applied together as a whole. In short, the sum of the whole outweighs the sum of the individual aspects. The application of those combined, integrated and holistic protocols and skill sets is what might be termed 'technical diving'.

Technical divers - those who dive according to a philosophy of risk mitigation, will always be perplexed as to why some might choose risk acceptance. The question is simply "why do a given dive in a dangerous manner, when it can otherwise be done with a high degree of safety?"

I've never seen a logical rationale to support a risk acceptance approach. I've only ever seen financial concerns, lack of commitment or ignorance as deciding factors in the acceptance, rather than mitigation of risks. I've seen plenty of divers attempt to justify risk acceptance for other reasons, but that justification rarely, if ever, reflected the real reason why they didn't seek to mitigate risks in the first place.

The worst justification is that spawned from a process of risk normalization. A diver conducts a dive with high risk acceptance - they acknowledge, even if not openly, that the dive is unsafe. On that dive, nothing goes wrong. So the dive is repeated. This causes them to began an assumption that there wasn't high risk acceptance in the first place. Exposure to risk becomes normal. Acceptance of risk is reduced, because the existence of risk is questioned. Thus begins a spiral of increasingly aggressive, dangerous diving - each of which reinforces to the diver that risk is not present... that warnings and recommendations are not valid. For some, with strong ego, the process affirms to them that they are very capable, safe divers... that the rules, recommendations and warnings do not apply to them.

Of course, this process only continues for so long that nothing goes wrong.

When it does, people get hurt or killed, because the underlying state is that the risks were present and did apply to them all along. The inevitability of a negative outcome existed all along and nothing was done to prevent it. The severity of the outcome... that just depends on how far down the path of risk normalization the diver had progressed.

Risk acceptance is a gamble. The odds may vary, but the reality remains that when... finally... those odds are not in your favor there will be terrible consequences.

 

[NAM001]

This is one thread that I have watched because of the topic of how the need for unexpected deco recovery, OW diving, agencies and human nature all come into play. I particularly like TSM's post 173. The idea of CMAS covering deco in basic is a good idea. It either instills the reasons to be aware of your times or provides an excuse to ignore them. I would think that ow should cover some limited deco information to the extent of getting yourself out of a potentially threatening unexpected obligation. Sort of like emergency deco recovery to the level of CESA understanding.

What would be a rule of thumb for such a situation considering the worst of all factors? Such as:
--A new OW that believes his training covers them through out the recreational range of 130ft.
--He possesses a log book with 10 dives in it.
--This diver has a buddy with 9 dives in his book.
--They have computers that they use with minimal understanding. IE depth gage and clock and tank pressure if integrated.
--Some period of time they discover that the beeping is their computer telling them they have entered deco/exceeded NDL and from that point they don’t understand the displays as deco displays are foreign to them.

I realize that any resulting rule of thumb will mostly be overkill for most dives but that is ok, because that is what a rules of thumb are. It is what is used when a lack of specific actions for a situation are not available.

Could we say something along the line of divide your depth by 3 and go to that depth (if greater than 20 ft) or 20 ft and stay for 3 times the time you think you were past ndl then proceed to safety stop for normal time plus an additional 3minutes and then spend 3 min going to surface. Then boldly call this a rule of 3’s.

So if a diver is doing a repeditive dive and finds he is past ndl by maybe 2 minutes at 80 ft he would go to 1/3 of 80 or say 30 ft for 6 min and then go to safety stop for 6 min instead of 3 and then to the surface slowly and end diving for the day.

Something like this would cover . What to do if you find yourself suddenly past NDL. A less than optimal solution for a prior failure but a process that is concequence limiting.

 

[Storker]

Isnt a suunto more like simulating the entire dive as itll put you in deco pretty much if youre snorkling?

Yeah, I know that the Suuntos are notorious for being conservative and that that's virtually a meme around here, but wasn't that ever so slightly over-the-top hyperbole? At depths below 20m, the NDL differences between PADI's RDP, Suunto's RGBM and the Norwegian navy table really aren't significant:

            NDL, min  
Depth, m    PADI RDP    RGBM    Norwegian navy table
10             219       170 
12             147       125          135
14              98        83 
15                        72           85
16              72        64 
18              56        53           60
20              45        42 
21                        38           40
22              37        35 
24                        30           30
25              29        28 
27                        24           25
30              20        19 
33                        15           15
35              14        13 
36                        12           10
39                        11           10
40               9        10 
42               8         9

One of the reasons why recreational computers can't be used for staged decompression diving is that they don't behave like real deco algorithms. I have read stories of dive computers racking up ridiculous amounts of deco when the diver didn't immediately march to the stop depth and stay there. Some of the computers do not give you any credit for offgassing below the mandatory (shallow) stop depth. Others will do as described, and clear as you ascend.

The Suunto RGBM algorithm will give you some credit for normal type deco stops, but it'll still scream bloody murder if you go into significant deco, and the 3m stop will be longer than for anything else I've seen. For my own amusement, I did a comparison of the Suunto RGBM, the VPM-B algorithm (free Android version of V-Planner, +2 setting), the Norwegian Navy table and the US Navy table for a 120 minute dive to 18m/60ft. The differences were... shall we say "interesting"?:

Depth, m   US Navy   VPM-B    No. Navy   Suunto RGBM    Suunto + No. Navy
 0             0        0           0          0              0       
18           120      120         120        120            120       
 9                                  5                         5       
 6                      6.8        25                        25       
 3            26       28          30        111             97       
--------------------------------------------------------------------------
Total time   149      157         183        234            250

 

[Rhone Man]

On pure square profiles the Suunto algorithms don't look too bad.

But Suunto are much less forgiving in a number of soft respects though: they punish you heavily for skipping a safety stop or ascending too swiftly; they don't compute off-gassing as fast during surface intervals; and if you are in deco they really punish you unless you stay as close to your ceiling as you humanly can (but woe betide you if actually you break the ceiling...).

 

[Storker]

OK, thanks for the info.

I wouldn't know, tho'. I dive conservatively, rarely ever ride the NDLs, have never exceeded the NDL, have never done more than two dives in a day and my SIs are generally well in excess of 2 hours. And since, after making the SS mandatory on practically every dive and paying close attention to really slow ascents from the SS leading to me hardly ever feeling any significant post-dive fatigue, I've concluded that I'm not going to push my computer's limits. Neither WRT bottom time nor WRT ascent speed. So that aspect of Suunto's conservatism has never limited my diving.

YMMV, of course

 

[victorzamora]

Here's how I see the thread:

OP: "I want to do X, Y and Z"

One tiny correction here. I'm the OP, and that's very much not what I meant nor is this what this thread was meant to be about. I just wanted to clear up that that is NOT my position at all.

Having said that, Scubadada has taken a more predominant role in this thread than I have as others with more experience than me have taken my side of that conversation. Andy, you definitely captured what HIS argument is as clear as day. Scubadada can dive how he wants, it's no bother to me....however I don't get his perspective as anything even approaching safe. He's attacked me as well as others for our online profiles not showing as many dives or as many certs as he believes necessary to have an opinion worth noting. My wife (just got AOW, no tech aspirations, <40 dives) truly believes that ANY deco is beyond what any rec diver should be incurring. I asked her what SHE would do if her computer went in to deco, and she responded with "I'd calmly ascend to like, 20ft or whatever the computer tells me. Then I'd go up SUPER slow from there, and be done for the day....because I'm NOT dumb enough to let that happen on accident, and if I let it happen on purpose it's because something went really wrong."

My point is that too many divers don't know what they don't know. A clear line *should* be drawn in the proverbial sand between Rec and Tec. Without the training AND equipment to do a dive safely, no amount of experience, hubris, or bravado will get you to the surface safely. Scubadada, the position you've taken is one of being bulletproof. "It can't happen to me. I'm better than that. I've done LOTS of dives." is simply NOT the attitude one should take as a Tech diver. I can tell you now I would've failed all of my Tech courses if I showed my instructor HALF of that attitude. I'm sure most/all Tech-certified divers can agree with me on this, but my Tech courses have shown me that no matter how good I am compared to the Rec crowd....I've got a LONG way to go before I become a "good diver" amongst the Tech crowd. That realization has kept me cautious, attentive, and always wanting to learn more and do better. It was a BIG TIME eye-opener, and I'm glad I had it.

 

[Tigerman]

Yeah, I know that the Suuntos are notorious for being conservative and that that's virtually a meme around here, but wasn't that ever so slightly over-the-top hyperbole?
...

Isnt this entire thread?