Is scuba gear life support?

[CG43]

CESA is a Hail Mary moment, full stop. You've f#@ked up and your last desperate chance is a swim to the surface.

Powerful words . I shouldn't have written CESA because E = Emergency implies an emergency. What I meant was CA = controlled ascent.

Cousteau writes about beginner diving training French Navy 1948 in "The Silent World".
"At the end of the course, the best graduates swim down 30 meters, take off all their equipment, and return to the surface without anything. The Baccalaureate is an enjoyable ritual."
I will continue this topic later; for today, it is too late.

 

[The Chairman]

Specifically, should someone not commence a dive to a certain depth unless they are confident in their ability to do a CESA from that depth?

I don't think I could CESA from a 1,000 feet back in a cave. Could you? Nah, but I'm still gonna cave dive.

 

[tursiops]

I don't think I could CESA from a 1,000 feet back in a cave. Could you? Nah, but I'm still gonna cave dive.

To be fair, he was specifically talking about recreational diving.

 

[The Chairman]

To be fair, he was specifically talking about recreational diving.

What's the fun in being fair???

 

[tursiops]

What's the fun in being fair???

I figure there is plenty to make light of in his suggestion without violating his premise...

 

[34109411]

But that's exactly what this man is demanding !!!
And if you want to dive deep, you have to train your ability to perform a CESA.

In the 1970s in Germany, an advanced diving certification included a free ascent from 30 m. This part of the test was removed because there were too many incidents.
At that time, we had a maximum ascent rate of 18 m/min, so the ascent only needed 1.5 minutes.
As a freediver, that was also a fun exercise for me. Back then, and even today, I believe that a minimum level of freediving ability is part of advanced scuba diving. Let's say a freediving depth of 18 m should not be difficult, then a CESA from 18 m is also not a problem.
Before the 30 m free ascent, a free dive to at least 20 m should always have been demonstrated first.

If the problem is that you have emptied your tank, for example in 50 meters, it still has 6 bar of pressure that you can use when ascending to a shallower depth. You can calculate an acceptable ascent, and you can also try it, which I have done. However, I would only recommend trying it to freedivers, as it is quite challenging.

I don't know if the exercises suggested by the man are very helpful. This is not mainly about learning movement patterns, but about physiological adjustments when one cannot breathe. For comparison, one does not learn long-distance running in a few days , but through frequent training the body adapts without us having direct influence . You should be happy, calm, and relaxed, even if you sometimes don't need to breathe or can't breathe . The redundancy you gain from this is sufficient for most recreational dives.

i understand still...

 

[CG43]

About CA or CESA from 30 m depth : continuation of post #29

It is extremely difficult to do even when you are prepared for it as part of an exercise. Also as a freediver you know that a freedive to 20m is a totally different animal to a ascent from 20 or 30m when you are stressed and out of air, wearing scuba. Performing this dive you are mentally and physically prepared. You breath up, you're wearing only fins, suit and mask, No drag, you're weighted to be buoyant from at least 5m deep. Compare that to an unexpected emergency swim when your heart rate is up and in addition you have the drag of bcd, regs and tank and you are weighted to keep you down comfortably at a 5m stop when your tank is low on air.

So there are different views on this. In Cousteau's case, these scuba beginners were selected twice.
1.) Every navy ship should have two scuba divers on board. It is not unlikely that this included spear fishermen or other freediver as well. 2.) Only the best of a course took this CA (CESA).

Let's start with buoyancy. A freediver has a total lung volume of 6 liters. At a depth of 5 meters, that's 4 liters, and at 30 meters, 1.5 liters. When he is equalized at 5 meters, he experiences 2.5 kg of neg buoyancy. If we add 0.5 kg for a thin neoprene suit, that makes 3 kg of neg buoyancy, and he will first be neutral again at a depth of 5 meters.
In the exercise, he starts neutrally and can very quickly stop swimming due to the expansion of air in his lungs and BCD.
In the worst-case emergency, he has completely exhaled and no air comes out. If he had taken 3 liters per breath beforehand and was balanced at a medium volume, he is only 1.5 kg too heavy.

The higher water resistance due to more diving gear is not so serious because the scuba diver should not swim to the surface too quickly due to the risk of DCS. That is the big problem, not reaching the surface like it is for the freediver.
The scuba diver has more oxygen in his blood plasma and other tissues, so the risk of an oxygen deficiency-related blackout is low. The CO2 may trouble him significantly, but a freediver, he can handle it.

The biggest advantage that the CA (CESA) scuba diver has over a freediver is that he only has to swim half the distance.

Now, if you consider all the advantages of the CA (CESA) diver compared to freediving, why were there incidents?
It seems to me as if with full scuba equipment the idea of holding your breath is not accepted by the mind of many scubadivers . The old Cousteau divers were in swimming trunks with 3 tanks, one regulator, mask, and fins. Water all around the body could enhance the diving reflex.
During a relaxed dive, I occasionally remove the regulator from my mouth and dive for a while without it. After all, my life shouldn’t always depend on scuba.
Before I climb out of the water with all the diving gear, I might still do two breath-holds.

 

[hammet]

About CA or CESA from 30 m depth : continuation of post #29

So there are different views on this. In Cousteau's case, these scuba beginners were selected twice.
1.) Every navy ship should have two scuba divers on board. It is not unlikely that this included spear fishermen or other freediver as well. 2.) Only the best of a course took this CA (CESA).

Let's start with buoyancy. A freediver has a total lung volume of 6 liters. At a depth of 5 meters, that's 4 liters, and at 30 meters, 1.5 liters. When he is equalized at 5 meters, he experiences 2.5 kg of neg buoyancy. If we add 0.5 kg for a thin neoprene suit, that makes 3 kg of neg buoyancy, and he will first be neutral again at a depth of 5 meters.
In the exercise, he starts neutrally and can very quickly stop swimming due to the expansion of air in his lungs and BCD.
In the worst-case emergency, he has completely exhaled and no air comes out. If he had taken 3 liters per breath beforehand and was balanced at a medium volume, he is only 1.5 kg too heavy.

The higher water resistance due to more diving gear is not so serious because the scuba diver should not swim to the surface too quickly due to the risk of DCS. That is the big problem, not reaching the surface like it is for the freediver.
The scuba diver has more oxygen in his blood plasma and other tissues, so the risk of an oxygen deficiency-related blackout is low. The CO2 may trouble him significantly, but a freediver, he can handle it.

The biggest advantage that the CA (CESA) scuba diver has over a freediver is that he only has to swim half the distance.

Now, if you consider all the advantages of the CA (CESA) diver compared to freediving, why were there incidents?
It seems to me as if with full scuba equipment the idea of holding your breath is not accepted by the mind of many scubadivers . The old Cousteau divers were in swimming trunks with 3 tanks, one regulator, mask, and fins. Water all around the body could enhance the diving reflex.
During a relaxed dive, I occasionally remove the regulator from my mouth and dive for a while without it. After all, my life shouldn’t always depend on scuba.
Before I climb out of the water with all the diving gear, I might still do two breath-holds.

If rec scuba diving were limited to navy seals, young and fit athletes, and experienced free divers who could safely CESA from any depth, there wouldn't be any scuba industry to speak of.

 

[paddydiver]

The biggest advantage that the CA (CESA) scuba diver has over a freediver is that he only has to swim half the distance.

But its not an advantage. The freediver is prepared to swim back up from whatever depth he had dived otherwise he is a suicidal diver not a freediver. The Freediver also does not have to breathe out on the way up to avoid a lung overexpansion. The freediver also does not have to attempt to control his ascent by releasing air from his bcd and/or drysuit on the way up. There is no comparison, one is a relaxed preplanned dive the other is stress coupled with a huge taskload.

In some things you say, I agree. It has been done and can be done. But, In the early days of recreational diving people learnt without bcds, breathing from regs that were far from easy, using heavy rubber fins. They were strong swimmers and developed strong lungs and muscles of the rib cage (despite all the smoking). As someone said above, if this was the criteria today there would be no recreational industry.

 

[lizardland]

Now, if you consider all the advantages of the CA (CESA) diver compared to freediving, why were there incidents?

Cousteau writes about beginner diving training French Navy 1948 in "The Silent World".
"At the end of the course, the best graduates swim down 30 meters

I think you've answered your own question. The "best graduates" of the average PADI Open Water course will more than likely be worse than the worst graduates of a naval diving course.

Personally I think freediving is fantastic for building comfort in the water. But I also think the CESA is looking at the wrong solution. Training should address how to not get into an out of air situation where the only alternative is to head to the surface with just the air in your lungs. In 30 years of diving I've managed to never be in that position despite doing a lot of stupid things fairly frequently so it's clearly not that hard to avoid. On the other hand, I've helped pull two people out of the water after doing CESA's for real who both ended up with fatal lung injuries.

I'm not convinced that CESAs value in the real world are worth the risks. I would love to see some figures on it if they exist.