The depth shall be 60, 60 shall the depth be, 61 is right out unless your AOW certified????

[dmaziuk]

...
If you are relaxed, take a few deep breaths and get neutral and then start the ascent.. 60 feet is pretty easy.
...

My point exactly: I thought we were talking oh s*it emergency below 80 feet. I quoted my horizontal breathholding swims as an example of being relaxed, prepared, in a non-emergency situation -- and I still get enough CO2 buildup to start pinging the breathing reflex at around 70-ish feet.

Edit and I'm not timing it, maybe I'll do that tonight, but it shouldn't be over 30 seconds, likely more like 20. Just to round this out let's say it's 120 feet per minute: 4 times the "bubble-safe" ascent speed and twice the "bubble-unsafe" rate. Meaning, if I'm coming up from > 80 ft at 60 fpm, I'll need a minute plus to do it, and my breathing reflex will kick in even before I'm halfway up. Even if I started relaxed, by the last 15 feet I don't expect to be: I expect to be fighting the urge to breathe.

As I recall before the SWBO one reason given to freedivers for never exhaling was: keep your mouth shut or you will inhale. I'm not so sure that for scuba divers "nothing will happen" is the whole story. I may have a reg in my mouth, there may be another breath in the tank at some point, but my basic assumption is if I inhale, I'm inhaling deadly poisonous dihydrogen monoxide.

 

[2airishuman]

I don't know which op you're using, but I have dived the Vandenberg several times. The op I used couldn't care less about Nitrox. They do want you to have an AOW or some other proof of similar diving experience. If you don't have it, they will still take you if you hire a guide that costs considerably less than an AOW and/or Nitrox cert. Again I would advise getting both certs if you are going to do a lot of vacation diving. It just makes life easier, but it's not mandatory for "one off" dives if you (the diver) are comfortable with the dives. None of this has anything to do with agency depth recommendations AFAIK. Good luck with your dives. Nothing against the dive op you've chartered. Sounds like you've done your due diligence before booking. Actually, IMHO, that's my first rule of vacation diving. Talk to the dive op in advance and know their rules. Their boat, their rules.

To be clear, the op I'm using will take me on the dive without AOW or Nitrox certs. But they'll require me to hire a guide, and they'll require me to use air rather than Nitrox. That's not the dive I want to do.

I learned exactly zero from the Nitrox class because I knew the material before I took it, and had dived Nitrox before I took it. But I needed the card, because I want to dive nitrox in a number of places that want to see the card.

All kinds of gatekeepers out there. Adds unnecessary cost and hassle for people who learn well without a formal class and who have enough sense to expand their experience gradually.

 

[2airishuman]

You will get more air from the tank because the tank was not actually empty when you started the CESA. The problem was that the regulator could not deliver air at that pressure. When you ascended to a lesser pressure, it could not give you a breath of air. We fail students in the CESA exercise if they take a breath in the last 5 feet; we should reward them for doing the right thing instead.

Doesn't work if the reason for the CESA is anything other than exhaustion of cylinder contents.

I've breathed down a cylinder to zero (in my living room) just to see what it feels like. There's all kinds of warning, at least with the regs I use. An out of air CESA would be much easier than a CESA resulting from an abrupt 1st stage failure, or in response to a 2nd stage problem like a mouthpiece coming off.

 

[boulderjohn]

I may have a reg in my mouth, there may be another breath in the tank at some point, but my basic assumption is if I inhale, I'm inhaling deadly poisonous dihydrogen monoxide.

Why is your regulator out of your mouth? It would seem to me that keeping a regulator in the mouth is a reasonably simple skill to learn. Are you assuming you will panic and do something stupid?

Doesn't work if the reason for the CESA is anything other than exhaustion of cylinder contents.

Such as....?

I am not implying that there is no other reason for your CESA. I am suggesting that pretty much all the other reasons for a CESA have other circumstances that may work in your favor. I had an argument with PADI about this very thing a number of years ago, and they made that same response. The example they provided was a burst second stage hose. If my second stage hose bursts, I should be able to breathe all the way to the surface. The only thing I can think of is an abrupt failure of the regulator preventing any air from getting through under any circumstances. That would be a pretty rare event.

 

[2airishuman]

Such as....?

- Abrupt internal failure of the 1st stage regulator (on the now nearly-universal upstream opening diaphragm regulators, this can be caused by delamination of the HP seat, breakage of the pin that opens the HP valve, or clogging by debris)
- Clogged passages in the dip tube or tank valve
- Mouthpiece separates from 2nd stage (you or I could switch to a secondary, or breathe from the 2nd stage without a mouthpiece, but PADI doesn't train people to do either of those things)
- Ripped diaphragm, folded exhaust valve, or damaged housing in the 2nd stage, an astute diver would switch to a secondary or ride the purge button, again not taught and not something everyone will figure out

I am not implying that there is no other reason for your CESA. I am suggesting that pretty much all the other reasons for a CESA have other circumstances that may work in your favor. I had an argument with PADI about this very thing a number of years ago, and they made that same response. The example they provided was a burst second stage hose. If my second stage hose bursts, I should be able to breathe all the way to the surface. The only thing I can think of is an abrupt failure of the regulator preventing any air from getting through under any circumstances. That would be a pretty rare event.

I have seen three separate firsthand reports of abrupt 1st stage failures on SB that led to complete inability to deliver air, although one was a reg that was far overdue for service.

 

[TMHeimer]

To be clear, the op I'm using will take me on the dive without AOW or Nitrox certs. But they'll require me to hire a guide, and they'll require me to use air rather than Nitrox. That's not the dive I want to do.

I learned exactly zero from the Nitrox class because I knew the material before I took it, and had dived Nitrox before I took it. But I needed the card, because I want to dive nitrox in a number of places that want to see the card.

All kinds of gatekeepers out there. Adds unnecessary cost and hassle for people who learn well without a formal class and who have enough sense to expand their experience gradually.

Agree on the gatekeepers. We keep adding "permits", "restrictions" on things the last few decades, scuba just being one of them. And these "rules" are rarely retracted. Relying on people to have good sense today rarely happens.

 

[John C. Ratliff]

...If you have a low on air ascent and can sip the expanding air from the tank, this is a HUGE crutch and will make the ascent much, much easier, but I don't think we can assume that there will always be a functioning regulator in all situations.

Practicing a true emergency swimming ascent is so DANGEROUS that it is not allowed to be taught (anymore), but people are being told that it is not hard and you wont pass out etc.. If I truly believed that "line" I would not be carrying a pony bottle on a lot of dives.

Why is a diver going to be able to calmly exhale one single breath of air on an ascent (in a CESA), but when he makes the same ascent on a pony bottle he will be on the verge of panic and will be breathing 50 times to cover the same distance?...

dumpsterDiver,

You bring up a great point, and one that is interesting to me. Today, as a result, I went to my local pool, Summerset West, which is a 25 yard outdoor pool (they are staying open late as our indoor pool is being re-fitted with a new roof and interior). My first length was an underwater swim using my mask, fins and snorkel. For fins, I used my Force Fins, which are somewhat less efficient than some other power fins. I took half a lung-full, submerged and swam the length underwater. Yes, I was getting the "running out of air" signal at the end of the swim, but I was able to make the 75 feet to the end of the pool. I did that once more in my swim today, using a full lung-full of air, and had no problem at all making it one length underwater. Now, think of swimming that length with three lungs-full of air.

Now, there are a few things that would inhibit my ability to swim that length. If I was in full scuba, and wore a scuba unit that was very bulky, and/or was in a dry suit, there may have been more problems.

I have a few advantages over others. My lungs can hold 6 liters of air (and actually perhaps a bit more). This was confirmed multiple times when I took a respirator medical exam for work. I also have been diving almost forever (since 1959, which is what, 57 years now). But I have a few disadvantages too, one being 71 years old next month.

I note in the quote above that you neglected to put the word, "controlled" in front of "emergency swimming ascent." That is a critical word. What we mean by "controlled" is that the diver is in control, is relaxed, and can simply swim to the surface. If the diver is panicked, then the ascent is not "controlled." To give an example, here's an entry from my dive log:

Sept. 17, 1975
Dive: Yaquina Bay for Subtidal Clam Bed Survey, Oregon Department of Fish and Wildlife
Average depth: 36 feet
Maximum depth: 39 feet
Visibility: 10 feet
Current in Knots: 0-2 (multiple dives that day, we were closer to zero than 2 knots
Remarks: Photography Dives--Ran out of air on last dive. Buddy breathed ~5 min--long enough to get the photos needed.

What I didn't say is that at the end of that dive, I did a controlled emergency swimming ascent (CESA) up the line to our boat. I say this not to brag, but to say that if someone is relaxed and comfortable, a lot can be accomplished.

This is a drawing of what we were doing in the subtidal clam bed survey. We would dredge out a hole 2 feet square (we had a ring of the correct diameter), gather all the clams, count them and determine numbers of different species (gapper clams verses cockles, etc.).

What we have now is a bunch of people who are not really relaxed in the water, who have passed a diving certification class, but don't have the water skills to actually cope with some of the emergencies that they might encounter. The diving industry is now selling courses that were in the past included in the basic scuba course, and saying that without these "advanced" courses they should stay inside of 60 feet depth. Do our "advanced" course, and you can go to about 100 feet. Do another course for "deep diving," and you can get to 130' and/or do decompression dives.

Obviously, if you dive deep, and make a dive requiring decompression, a CESA is not really an option (or at best is a bad option), as the risk of decompression sickness is great, greater than the risk of a lung over-expansion accident. Most or perhaps almost all these "deep divers" don't have an alternative set up for helicopter evacuation and recompression, so this as a really bad possibility.

The same goes for overhead environments (caves, wrecks, being inside a coral reef, etc.). If access to the surface is not available immediately, a CESA is not an option. This is when the pony bottle, alternate air supply, etc. is needed, in my opinion.

But for my 25-30 foot dives in my river, I really don't need to bulk up my equipment, break streamlining (in a river with current) to dive safely. The CESA is a ready option.

SeaRat

 

[boulderjohn]

The diving industry is now selling courses that were in the past included in the basic scuba course, and saying that without these "advanced" courses they should stay inside of 60 feet depth. Do our "advanced" course, and you can go to about 100 feet. Do another course for "deep diving," and you can get to 130' and/or do decompression dives.

Can you give examples of concepts taken out of the OW course and put into later courses? Be specific--what was in what OW course formerly and when was it taken out? To what course was it added?

The AOW course was created by Los Angeles county in the mid 1960s to give divers exposure to different types of diving--it did not take anything out of the OW course at the time. We have just seen that the recommended depths have not changed much at all over the decades. Can you give a specific example of the kind of change you say is going on now that occurred in say the last 4 decades?

 

[dmaziuk]

Now, think of swimming that length with three lungs-full of air.

Ah, but I think you said yourself that it's not the air you have, it's the CO2 build-up that triggers "running out of air" signal. That's kind of what I was getting at with the O2 reserves in the bloodstream and tissue: because of that reserve you may not even need the air to keep going, but you'll still get an urge to breathe that you'll have to fight on the way up.

I did my OW checkout CESA from the bottom of the lake @ some 25-30 feet in 7 mm suits and weighted accordingly -- no problem there. As you say, shouldn't be a problem from that depth.

 

[John C. Ratliff]

John,

Is there a link to the current PADI/SSI or other OW courses that I could use to compare with the NAUI course workbooks I have from the 1970s? If so, I could make such a comparison.

My comment above comes from the discussion on this thread.

SeaRat

PS, I just looked at a PADI site where the different courses are shown. The PADI Open Water Diver course uses dives only in "Confined Water" and includes 31 hours of required instruction, including the 4 open water dives, I believe. I'm not sure what "Confined Water" means, but it seems that the "Advanced Open Water" course requires another 15 hours of instruction, including "5 scuba dives." So far, I have not found a breakdown of what the courses involve by teaching subject.