Faith diving and magic?

[MauiScubaSteve]

I think a 60 feet per minute ascent rate is appropriate for emergencies, at the very least below say 50 feet deep, and if the recreational diver is making "no stop" dives the 3 minute SS is not really necessary in an emergency, IMHO.

This thought process seems to me to be potentially more harmful than helpful, in that if your emergency is that you ran out of air, that implies you were pushing your NDL. In most cases, that means your fast tissues are going to be on the high end of saturation. Increasing your ascent rate AND skipping a safety stop may be a great way to get out of the water with the minimal amount of gas usage ... but you're pushing the risks of a Type II hit pretty high.

I'd say you really have to base your ascent rate on the amount of available gas at that point, and don't push your risks any higher than you have to. If you have the gas, keep your ascent rate within recommended limits, and do your safety stop. If you don't ... well ... even a Type II hit is better than drowning ...

... Bob (Grateful Diver)

If a diver is calculating "rock bottom" I would contend that "kind" of diver is very unlikely to "push NDL's" and "accidentally run out of gas." Are we not mostly talking about "catastrophic failure" with this type of planning?

I am still confused as to how an experienced, knowledgeable diver "accidently" runs out of gas, necessitating the emergency use of "rock bottom."

 

[MauiScubaSteve]

Now I'm going to throw some stones; how can a responsible scuba instructor say this with a clear conscience?

"all the diving in Coz is deep followed by multi levels up. so it is typical for a computer to show deco at depth then clear 1/2 way through the dive."



Are you really saying that recreational tourist divers "typically" dive their computers into deco when diving Coz?

Still hoping the OP will address this post...

 

[Rick Murchison]

...I am still confused as to how an experienced, knowledgeable diver "accidently" runs out of gas...

Uh, see post #1...

Rick

 

[DevonDiver]

"all the diving in Coz is deep followed by multi levels up. so it is typical for a computer to show deco at depth then clear 1/2 way through the dive."

Still hoping the OP will address this post...

Me too... it's not a comment that I'd expect to hear from any well-trained recreational diver and neither is it an accurate portrayal of how most recreational divers perform.

I can't think of any reference to 'inevitable deco' in the course materials for the Multi-Level diver course...

I guess as long as the deco would clear 1/2 way up on an 60ftpm direct emergency ascent, it'd be ok?!?!

 

[MXGratefulDiver]

If a diver is calculating "rock bottom" I would contend that "kind" of diver is very unlikely to "push NDL's" and "accidentally run out of gas." Are we not mostly talking about "catastrophic failure" with this type of planning?

I am still confused as to how an experienced, knowledgeable diver "accidently" runs out of gas, necessitating the emergency use of "rock bottom."

I think you don't understand what "rock bottom" means.

The definition of rock bottom is having adequate gas reserves to get you and your dive buddy to the surface while making an orderly ascent ... with appropriate stops ... from a given depth.

So any diver who's using rock bottom is ... by definition ... diving appropriately with a dive buddy AND maintaining appropriate gas reserves for both of you. Therefore if there's a catastrophic failure, they aren't going to "blow and go" ... they're going to share air and make a controlled ascent. There isn't a need to exceed recommended limits ... or to blow off a safety stop ... because if you're using rock bottom you have adequate air to make the ascent within the accepted safety standards.

That's the whole point of rock bottom ... to always make sure you have adequate gas reserves to avoid the need for an emergency ascent.

Therefore I fail to see your point. Making a 60 fpm ascent and blowing off your safety stop when you don't need to would be a stupid thing to do ... you're just increasing your risks unnecessarily ...

... Bob (Grateful Diver)

 

[SailNaked]

Well I am not really sure I understand the question and I think it is just bait, but when diving to 100+ft along a bottom in current, it is easy to exceed the NDL by a little and it clears quickly.
As far as emergency planning it usually happens with more than 1.5k air in both tanks and would not be an issue if there were a failure while under the obligation of a minute or two.
what made this dive a problem and why we ran out of air is that our computers wanted us at 10ft to work out the obligation and did not give us any credit until we were at near 10ft. on previous dives the obligation was gone at 60ft and did not come up with us. We spent over 20 minutes working on the deco. basically arguing with my watch

I was over my NDL on the bottom for about a minute that resulted in an 8 min obligation, I dont know how far over my wife was over but she had 14 minutes when we left the bottom and after 20 min above 15ft she still owed 5 minutes. I know we spent 20 minutes on deco because of the logs on my computers, at the time it took me some time to realize that we were not getting full credit.


yes the planning in Coz is really flexible, dive till 750 then head to safety stop and leave with 500, we are usually out of the water with 1k if we stay with the group. bottom is approximate, variations of 20-30ft are common.

yes we plan dives to 130, there are at least 2 dives that I have done in Coz that have that as max depth and real max depth is usually 135 to 140, and my tables say we can stay there for 8 minutes, my understanding of tables is that max depth total time, so a 58 min dive to 130 exceeds the NDL by 50 minutes. how exactly do you enter that in your log book?

Real life, 130 for about 4 minutes, up to about 100 for another 5 minutes then up to 80 for 20 minutes then up to 60 till your at about 750 and then to your stop for 5. and if for some reason the DM decides to kill the two huge lion fish at 130 and takes an extra 2 minutes doing it, then your watch is going to complain for a few minutes during your dive. If you have not been there then get off your horse and go see it, great diving for all levels of diver.

I know I did not plan the last dive of the day very well, and I did not expect to hit a limit on it either. I did not look at my watch much because of my assumption that we were on a shallow dive. all mistakes that I have admitted. but please do not use it to make a case for carelessness on all dives.

How does an experienced diver ever make a mistake? um well they just do. (and I do not claim to be experienced yet, I have not made enough mistakes).

I went back and looked at my log,

the average depth was 36ft. the total run time was 77 minutes, we hit deco at 50m and we had a 27m ascent. I think as far as gas planning goes this is outside the normal. max depth was 58ft when I went to get my wife.

 

[fdog]

I understand what you're saying, that this kind of dive planning is de rigueur for Coz.

Doesn't make it right. Might be a big reason that Cozumel has the highest DCS rate around?

If I did that kind of planning, my dive buddies would stop diving with me - and rightfully so.


All the best, James

 

[TSandM]

I just think the point being made was that going into a little deco, with the expectation it will clear on ascent, requires a high degree of confidence that you will not require a direct ascent to the surface during the period of the deco obligation. In other words, once you have seen that number click over into a deco obligation, you'd better be able to solve whatever problems arise where you are, because the risk of surfacing as a result of a gas problem (or anything else) has gone up significantly. How much? That's the question the thread started with.

 

[SailNaked]

In diving we make many assumptions all the time, we assume our tank will not explode, we assume we can reach our buddy to breath his air, we assume the nurse shark will not bite us in the arse.

when we dive with planned Deco we have 4 tanks 4 regulators, 4 BCDs, I am not making an argument for permitting Rec Divers to accept any deco obligation, any more than I think a new diver should exceed 60ft.

the tables state that the safety stop is not optional for all dives >100ft or within 3 PGs of a limit. so rec divers are accepting a deco stop with one tank and one regulator every time they go past 100ft.

What I am saying is that we are playing with fire, when we use a computer. they are great devices, they manage the many data points going on in a dive and give us a readout that is easy to understand and use.

to accept a small deco obligation that is no greater than the safety stop does not seem to me at my diving experience to be an excessive risk even with one tank and one buddy (at the same experience level).
this is back to faith and magic, faith in a computer is like believing in magic for me. I have faith, and I believe but I still question.

 

[InTheDrink]

I don't believe any longer that things will go right, whether with 4 tanks or 1. Actually I use just two now, even on shallow dives as I think the risk of consequences of failure are too great, even if the chances are low (not remote tho).

I dived in Cocos a couple of years back and we all went into deco frequently and I ended up doing a lot of unintentional solo diving (my instabuddy was a pro camerman with an appetite for risk - had to donate to him on one occasion and was ready to on lots more). 40m dives, 10, 15 mins of deco, solo, some big animals around. Big current and surge sometimes.

Since then I want to know that whatever problems I have I can solve them underwater. Only downside is ive hurt my back lugging those damn twins.

Sounds like you've learned your lessons for your dive. Move on and don't stress too much about those perfect armchair divers that have never made a mistake themselves.

And definitely, where possible, sail naked.
J