Tough Buddy Separation Problem

[Blackwood]

Depends on the buddy...

Do you know him well enough to know whether he would actually abide by your "agreement" to not go inside the wreck? Do you know him well enough to know whether he would get narced at that depth and forget your agreement? Do you know him well enough to know whether he's got the skills to prevent himself from getting swept into the wreck inadvertantly by the current?

If you know the answers to these questions, then you have a pretty good handle on the relative likelihood that he is NOT inside the wreck.

The vast majority of the time, I dive with people out of the same group of about 8-10 folks. We've all had similar training, and embrace a team mentality.

As such, if I were ever to find myself separated, I'd consider it to be an extraordinary situation. I can't fathom one of my dive buddies making any change to the dive plan (be that ascending, deciding to do a little minor penetration, etc.) without [1] signaling me and [2] waiting for my agreement.

In my mind, chances are good that if we get separated, something is very wrong (narcosis, medical issues, what-have-you).



If I happened to be paired up with some instabuddy on a vacation dive, my reaction would be starkly different than were I diving with one of my own.

 

[Blackwood]

The "best plan"... the best plan is what years of experience by hundreds of divers had evolved into and is taught in dive classes... "Look for one minute and then surface safely"...

The thing is I think you're looking for some sort of universal "better mousetrap"... and you won't find it because of precisely what we experience on SB all the time... there are no limits to the extent of "what if" scenerios.

Plans are developed based on the highest probabilities... the highest probability of the nature of the problem... the highest probability for success... the highest probability for minimum collateral damage... the highest possibility for the average diver to employ the plan successfully... etc.

I don't believe for one second (hah) that the "search for one minute" rule is the outcome of a scientific study of probability and outcome.

"Hey Bob, I'm writing the standards. How long should we say to search for a lost buddy?"

"Simple, Jerry. The limit as mistakes approach infinity of the permutation of collateral damage mechanisms raised to the root sum square of success probability is one. The units are minutes."

No, I imagine it was a much more random decision than that. The agencies needed something for their standards, and they know that their training methods lead to divers surfacing at the first hint of trouble, thus a separated buddy team is the likely result of one buddy surfacing without the other, so there isn't much point to searching long.

 

[Walter]

The term has never confused me. Required: Do it. Safety: For your safety. Stop: Stop ascending and hold for the recommended period of time. What is confusing about this?

It doesn't confuse me either, it's a decompression stop. A decompression stop is a required stop on ascent to allow off gassing. A safety stop is an optional (although highly recommended) stop on ascent to allow off gassing. A "required" safety stop is a decompression stop.

 

[Blackwood]

It doesn't confuse me either, it's a decompression stop. A decompression stop is a required stop on ascent to allow off gassing. A safety stop is an optional (although highly recommended) stop on ascent to allow off gassing. A "required" safety stop is a decompression stop.

There is no functional difference between a decompression stop and a "required" safety stop. However, there is a difference.

The former is required by the decompression model, the latter by whomever annotated the table.

It's clear which one is more important than the other.

 

[TSandM]

Reg, did you get the "Deco for Divers" book by Mark Powell? Reading that, I think, will make the whole idea of "required safety stop" a little clearer.

The fact is that, as the product of depth and time increases, the nitrogen loading increases, and the desirability of increasing the time from depth to the surface increases. The likelihood of symptomatic DCS if the time is too short also increases. At some point, the probability of DCS if you don't do some stops becomes close to one. Dives within the recreational range of depths and times will not reach that point. And, of course, nobody is doing any studies to give you really good data on what the DCS probability for a given depth, duration, and ascent time IS. So each of us has to use his own knowledge of how the models are constructed to decide where the ascent protocol may be violated in exigent circumstances, and some of that will depend on the individual's risk tolerance, and perception of the urgency of the situation.

 

[bleeb]

The term has never confused me. Required: Do it. Safety: For your safety. Stop: Stop ascending and hold for the recommended period of time. What is confusing about this? Sure there are allegedly "safety stops" that are "optional." I don't even know what that means without training to understand when it is better to get out of the water without a safety stop.

[fireproof suit]

Since this has become part of the discussion, it might be helpful for us to agree on a few definitions, just so everyone is using the terms the same way for the sake of this discussion. Although I think I've captured how many people use the terms, not everyone or all agencies necessarily agree completely, so don't assume these are universal definitions.

Recreational diving (diving within recreational depth limits, generally 130', and within NDLs) includes the implicit assumption that you can always ascend directly to the surface without stops, with 'minimal' chance of a problem.

Once you exceed recreational depth or time limits, you're into decompression diving, that is diving where stops are mandatory (or other profile shaping techniques such as ascent rates) or else bubbling sufficient to cause clinical symptoms is 'probable'. Generally, most tech-oriented instructional agencies strongly recommend/require redundant breathing gas supplies and regulators on each diver, since the failure rate is frequent enough to be an issue.

Most people define a safety stop as being a stop which is always optional (i.e. not mandatory), although highly recommended. As some of the researchers and originators involved have posted elsewhere on SB, quantitatively measured, safety stops in themselves do not appear to have a large or maybe even measurable effect on the frequency of DCS. However, there are theoretical reasons to believe they may have some benefits, and given the difficulties of measuring or even determining the effects on humans, most people use them as standard practice. They haven't always been there, there was some debate when people started using them, and some people don't believe in them. Some SB members have described in the early days how a large part of the value of the stop was actually to help make sure ascent rates stayed below table assumptions and make sure people were under control before undertaking the most critical part of the between 15-30' and the surface.

Part of the conflict in terms is created when you see the term decompression. All dives involve pressure change and therefor decompression, but for most people, the term decompression stop means a mandatory stop.

The biggest conflict in this thread seems to be caused by the term "mandatory safety stop". Quite a few people are of the school of thought that if the stops are mandatory, you're no longer recreational diving since you can no longer ascend directly to the surface if there are any problems (gear or otherwise) and you should have redundant gas supplies and regulators. However, if the table publishers are including these as a way to create additional safety margin and not a true absolute requirement, then some would argue that it really is a safety stop, and that the term "mandatory" is not in line with how the majority of divers with the more extensive technically training use the term.

[/fireproof suit]

 

[Reg Braithwaite]

Reg, did you get the "Deco for Divers" book by Mark Powell? Reading that, I think, will make the whole idea of "required safety stop" a little clearer.

Please don't confuse my explaining what I think PADI means by the term "required safety stop" with my thoughts about decompression or with my understanding of how safety stops got added to the tables in the first place. I have some opinions about what kind of deco works for me gathered from reading and talking with mentors and a from a small amount of experience doing deep recreational dives. This has led me to have opinions about PADI's tables and protocols, but the one that matters with respect to the safety stops is this: If you choose to dive according to PADI's protocols, then you plan for and execute all required safety stops.

 

[scubadada]

There may have been. However, my response was to the scenario (and question) as it was actually posed - not whatever I could dream up on my own.

Nowhere, that I read, did the OP say anything about a pre-dive discussion concerning any alternative "lost buddy" protocols. Had any such information been present in the OP, I may have given a different answer.

In other words - you do the best you can to follow the plan, whatever the plan is. Lacking a plan (as in the OP), fall back to your training and the standards that have been taught to you - whatever that training and those standards may be.

Cheers!
ND

Point well taken, you're right. When there is no plan you must fall back to the most univerally accepted default.

Good diving, Craig

 

[scubadada]

It doesn't confuse me either, it's a decompression stop. A decompression stop is a required stop on ascent to allow off gassing. A safety stop is an optional (although highly recommended) stop on ascent to allow off gassing. A "required" safety stop is a decompression stop.

I believe the safety stop might also have been created to get divers to slow their overall ascent rate, particularly in the critical last atm between 33 ft and the surface. ScubaBoard members who participated in table creation could probably comment on this.

Good diving, Craig

 

[TBURKE]

I learned how to dive on the Jersey Shore in the early 80's. Worked my way up to NAUI divemaster.
We dove square profiles. (no computers) Also our tables still gave you 60ft for 60min.
Occasionally people would get bent. I don't know when it was started or by whom, but we started using a "safety" stop to build in a little wiggle room into the tables. This was before DAN said a safety stop was a good idea.
Back then we had a formula for making an educated guess at our deco obligations if our equipment took a crap and left us hanging. (yeah, I know) That happened more than it happens now. That formula was VERY conservative. We all believed that too much deco time was better than too little.
I remember a PADI instructor yelling at one of his former students because she did a safety stop while diving with me. He threatened to pull her card for doing a deco dive and I think he said something about burning in hell.
Times sure have changed.