Dive Dangers; The Differentiation between "SOLO" and "BUDDY"
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Vladimir,
What I detailed might be treated as a template for considering the various possibilities. Inserting/replacing the various probabilities and conditional probabilities, and reconsidering the assumption of statistical independence, just might reveal some enlightening surprises regarding the respective likelihoods of the two scenarios.
Safe Diving,
Ronald
P.S. My probability theory is pretty rusty, so carefully check what I've done!
Statistical independence clearly does not apply in the case of buddy diving. For example, if the event is driven by a difficult environment (high current, big seas) since both buddies are subject to the same environment. Furhtermore, as soon as one buddy goes OOA the probability of a double OOA increases. It increases dramatically if gas planning was not performed- and it rarely is. I've seen it happen with my own eyes more than once. That's why tech divers are taught the rule of thirds and gas matching, GUE teaches rock bottom, etc. etc. Statistical dependence is also demonstrated by the previous example of siltouts in overhead diving.
Even assuming statistical independence, the example given assumes the failures are completely random and that every dive has an equal probability of such a problem. This goes against common sense. Some divers are a danger to both themselves and others, due to poor skills, poor attitude, lack of recent experience or whatever. I believe they have a higher probability of a bad event than a competent diver with a good attitude who dives frequently. Even equipment failures are not completely random since well maintained and recently used gear fails less often than poorly maintained, infrequently used gear.
If the dive plan accomodates a team, then by all means give me a competent buddy. A redundant brain is actually useful sometimes and diving with a good buddy is a lot of fun. But don't give me an incompetent nincompoop diving with gear that hasn't ever been serviced and has been dry rotting in the garage for 5 years.
Jaydubya,
Yes, this is the type of thing I was thinking of, too. As another example, when buddy divers are diving in very cold water and one has a free flow and shares air with the second diver using the second diver's only first stage, then there's probably an increased likelihood that the second diver's reg will free flow, too.
For those whose probability theory is a bit rustier than mine, recall that "Statistical Independence" allows Pr(A&B) to be computed as Pr(A&B) = Pr(A) x Pr(B), and Pr(AUB) to be computed Pr(AUB) = Pr(A) + Pr(B) - Pr(A) x Pr(B). In general, Pr(AUB) and Pr(A&B) can NOT be computed this way if events A and B are NOT statistically independent. In general, Pr(A&B) must be computed Pr(AUB) = Pr(A) + Pr(B) - Pr(A&B).
Also recall that probabilities must be assigned coherently. They cannot be assigned willy-nilly. A Venn Diagram is useful for keeping the assignments coherent.
Keep the above two things in mind as you work through various choices for the probabilities in my detail in my earlier post.
Have fun!
Safe Diving,
Ronald
Barracuda2
Contributor
Must be my age or something; This whole thread has turned into a foreign language to me. i feel like Charlie Brown when his teacher is talking to him; "wa-wa-wo-wa-wa-wo-waa. That's ok, you guys seem to know what you're talking about.
Barracuda2
Contributor
John_NZ
New
I did my first solo dive about a month ago. I have only done 14 dives but this was the first dive that I actually felt safe doing for the following reasons:
1. I had all the time in the world to think and consider everything I was doing. No trying to keep up with a buddy, no worrying about what they are up to, no stress of loosing them and what to do if I did lose them.
2. No silt, no mask kicked off my face, no fins pulling my reg out of my mouth.
3. Total self awareness - because there was no possibility of a buddy rescue I knew I could not be complacent. This I think caused me to dive better and more safely.
In only 14 dives I have had people kick my face, one person lost their weights and grabbed my hoses to stop themselves flying to the surface. Some people are not well matched physically - some will be too fast, or too slow.
I am new, and so probably those with more experience could pull apart my opinions, however I think having so few dives under my belt may give a point of view that others don't have.
Btw, I was only diving in 16 meters of water on a sandy bottom looking for scallops so the risk was comparatively low.
1. I had all the time in the world to think and consider everything I was doing. No trying to keep up with a buddy, no worrying about what they are up to, no stress of loosing them and what to do if I did lose them.
2. No silt, no mask kicked off my face, no fins pulling my reg out of my mouth.
3. Total self awareness - because there was no possibility of a buddy rescue I knew I could not be complacent. This I think caused me to dive better and more safely.
In only 14 dives I have had people kick my face, one person lost their weights and grabbed my hoses to stop themselves flying to the surface. Some people are not well matched physically - some will be too fast, or too slow.
I am new, and so probably those with more experience could pull apart my opinions, however I think having so few dives under my belt may give a point of view that others don't have.
Btw, I was only diving in 16 meters of water on a sandy bottom looking for scallops so the risk was comparatively low.
DevonDiver
N/A
John,
Your confidence in the experience seems based on a single dive, where everything went right. I've done ~4800 dives...and from that experience have learned to base risk assessments on when things go wrong. Basing presumptions upon the best-case scenario is a timebomb.
Your confidence in the experience seems based on a single dive, where everything went right. I've done ~4800 dives...and from that experience have learned to base risk assessments on when things go wrong. Basing presumptions upon the best-case scenario is a timebomb.
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