Basic Training + Planning

[261311]

Thanks xyrandomyx for the link, that will help a lot.

Makes sense as per comfort, I just associate added depth with added risk, that's why I wondered if there was a mid-level course rather than the deep diving course that seems to be ~130ft (no where near my ability or comfort to participate in extended learning at the moment). I'm interested in wreck diving and as we're aware- they're not always so shallow. A lot seem to be in a 80-90ft depth around me so I want to make sure that if I have the skills and confidence, that what I'm doing is safe. One thing that does make me scratch my head is dive tables in that if PADI recommends 60ft max depth, and if air becomes toxic past ~100ft, why include the dive tables up to 140ft? Just conflicts as per not teaching proper deco theory if they're going to readily provide a table for that. Frankly any of the depths that REQUIRE safety stops at any ABT I'd be more than nervous about without further instruction. It seems people who go to those depths anyways don't necessarily like to depend on the tables anyways, they would rather personal calculation and computers. Oh well.

@Wart, that's alright about bar/ psi. I understand the conversions I am over thinking this, especially with my current experience. It's part to my excitement, just trying to make sure that what I'm learning is correct and safe. No alarms have gone off in my course that what I'm learning is wrong, or incomplete but I do like to do my checking and extra homework.

 

[Lorenzoid]

261311, consider taking the PADI (if you wish to stick with PADI, that is) Deep Diver course. Like many PADI courses, it doesn't certify or qualify you to do anything, but it does teach you some things that should become more relevant as you dive deeper (PADI says "deep" is 60-100 feet). Sort of the same way the PADI Wreck Diver course doesn't certify or qualify you to dive wrecks but rather teaches you about hazards that you might not have considered. Yes, it's the modular approach, and even these sometimes derided courses can have some value, in my opinion, by showing you what you didn't know you didn't know, so you at least know what you will have to study further if you want to pursue such specialties in earnest. In my Deep course, the instructor touched on gas management and emergency decompression procedures, had us calculate SAC rates, give nitrogen narcosis some more thought, etc.

You should consider the Enriched Air (Nitrox) course as well. You will gain a better understanding of oxygen toxicity, which is what I believe you are asking about when you mention "air becomes toxic past ~100 ft" (which is not quite so, of course--maybe you're confusing nitrogen narcosis with oxygen toxicity?). I would recommend taking the Nitrox course as soon as possible.

I believe the answer is, as others have pointed out, that PADI does teach most of what you seem to be itching to learn, but that it's taught in a modular way in separate courses. Not to mention that you're free to study on your own whatever you wish. I don't think the modular approach is so bad. We don't see OW divers dying all over the place (that is, the current rate of injury seems to be statistically acceptable to enough people in our society that there's little demand for change). So the basic OW course seems to be fulfilling its purpose.

 

[Jim Lapenta]

My advice is to forget about staying with one agency. Find an independent instructor that will tailor a course to your needs. It doesn't even have to result in a card. What you want to look for is an instructor that has some tech certs and does some technical dives. And uses that knowledge and experience in their advanced classes and makes sure that you know when dive planning actually starts. And it's not when you get to the site. Dive Planning begins when you actually make the decision to dive. Gas planning also begins then.

I did a presentation on the importance of dive planning last year at a show. I was amazed, shocked, and saddened to talk to a number of divers who attended who never heard that. They got the be back with 500psi, use thirds (incorrectly for most of them), and watch your gauge. And a few actually were told to make sure they pay attention to the DM and what he/she does. WTF?

A number of OW instructors don't know how to plan a dive. They were never taught to. They never really had to. At least to the degree that I consider dive planning to be needed. They regurgitate the nonsense they were told and had reinforced in their DM and instructor training. It's why I feel no one should get a DM rating let alone an instructor rating without having taken at least one tech course. Even a good intro to tech will start with an analysis of why divers die.

In many cases it's due to piss poor planning. Once that's looked at then you look at how to really plan a dive. After going through some of that myself I put it in my OW course. People are told that poor planning kills new divers. We look at how and why. Then we go over the proper way to plan dives. Locally that means even figuring out who brings the after dive snacks. If going on trip your airline reservations are part of the dive plan. As is calling the op you'll use to see what types of dives they'll likely be doing. Not waiting til you get there to find out.

 

[Kevrumbo]

A Quick Contingency "Rock Bottom" Calculation and Gas Plan Estimate for Open Water for a deep dive to 30 meters to illustrate why beginners/novices should NOT be going to these depths beyond 18 meters:

For a single 11 litre tank (AL80), a total of 11 litres/bar metric tank rating and a diver's volume Surface Consumption Rate (SCR) of 22 litres/min -same as a pressure SCR of 2 bar/min*ATA (divide 22 litres/min by 11 litres/bar)- using an example NDL air dive to 30m (4 ATA) depth in Open Water.

Emergency Reserve/Rock Bottom pressure calculation, from 30 meters with one minute stops every 3 meters to the surface,
-->Just "tally the ATA's":
4.0
3.7
3.4
3.1
2.8
2.5
2.2
1.9
1.6
1.3


Sum Total: 26.5


Multiplied by 2 bar/min*ATA equals 53 bar Rock Bottom absolute reading remaining on your SPG. --this also happens to be the pressure in bar needed for one person in an emergency contingency to reach the surface with the above minimum decompression ascent profile.

So ideally for a two person buddy team, multiply 53 by 2 which is 106 bar for both to reach the surface (sharing in a buddy Out-ot-Gas contingency).

But realistically, for two experienced divers stressed: 106 bar plus 30% of 106 bar equals 138 bar Rock Bottom SPG reading.

For two novice divers stressed: 106 bar plus 100% of 106 bar equals 212 bar (200 bar is the standard starting pressure for a full AL80/11L Tank!!!)
--->obviously then, two novice divers on single 11L tanks should not be diving to 30m for any significant length of time. . .

 

[TSandM]

Air doesn't actually become toxic below 100 feet. Narcosis becomes noticeable below that depth, but narcosis susceptibility varies, and how important it is depends on the complexity of the dive. A lot of people dive air in the 100 to 130 foot range, although to me, it's low yield diving, since your bottom time at those depths is so short. Most of the dives I've done that have gone that deep on air have been big check-mark profiles, where the excursion to 130 is very brief (usually to look at one specific critter) and then the rest of the dive is done more or less as a steady ascent.

You are actually quite wise to recognize that, the further you get from the surface, the more risk is involved, and the less desirable it is to view the surface as the best solution to problems. It is a very good goal to have enough experience to be very comfortable with your gear and with all of your emergency procedures, before you find yourself trying to handle an issue at 100+ feet. For example, if you have a freeflow and the noise and reduced vision affects your buoyancy control on a 30 foot dive, that's one thing; if it does the same at 100 feet, you have a lot more nitrogen loading, and a much longer way to go to get to air. How you would handle the situation might be different between the two dives, and the amount of control you need to cope with it safely is clearly greater on the deeper dive.

There is a class progression that "gives" you greater and greater depths -- AOW "gives" you dives to 100 feet; Deep "gives" you diving to 130. But training is only one part of the picture. Diving and experience is the other. I'd feel much more comfortable taking someone who was AOW, but had been diving and practicing regularly, on a 100 foot dive, than I would someone who had the Deep specialty, but wasn't diving regularly, and hadn't flooded and cleared a mask since class.

And, of course, the best way to cope with a problem is to prevent it in the first place. I believe you've already been given the link to NW Grateful Diver's gas management article. Planning your gas supply, and understanding what your likely available time at depth will be with the tank you have, is the first step to not having a gas urgency/emergency. Having a good dive plan, and going over it in enough detail with your buddy to make sure both of you not only understand what you are (and sometimes are NOT) going to do, and how you are going to communicate while you are underwater, is another way to avoid issues. Doing a thorough and mutual gear check will prevent a lot of stressful events in the water (and this is the FIRST thing I see everybody jettison when they finish their open water class, never to take it up again).

Understanding diving in the detail that your curiosity is demanding is not going to come from the standard recreational diving curriculum. You can buy the Encyclopedia of Recreational Diving, which has a lot of information, but it still won't go into the depth (so to speak) that you want. That kind of education is unfortunately pretty much reserved for technical training at this time, with the exception of a couple of agencies that approach recreational diving from a technical point of view, and a few independent instructors who augment their classes with that type of information.

 

[drrich2]

Original Poster:

A few thoughts. My general impression is that you are more intelligent and analytical than the average for the general population, and enjoy learning new knowledge and understanding a task at hand well.

To be blunt, many students are dumber than you, don't care as much as you, and intend to 'follow the leader' on guide-led tropical tour dives in benign conditions, at least to start out. And even some fairly smart people may have such aims.

Also, Discover Scuba Diving is a course that gives a recommended depth limit of 40 feet, if memory serves, and doesn't qualify you to dive without a dive professional present. So, you and a buddy can't go practice at the quarry without your instructor, that sort of thing. If I understand correctly. And a lot of those guide led tropical tourist dives are to depths over 40 feet deep (some readily get past 60 feet).

And of course, OW is the basic level at which one becomes (officially at least) a 'real' diver. And people want that for themselves.

Bottom Line: People like you have ample opportunities to build on their knowledge base, via private independent study and structured formal instruction. And other people can get quickie cert.s, follow the leader in aquarium-like tropical conditions & look at the pretty fish and coral.

Something for everyone, I suppose.

One criticism often leveled is that a lot of the latter folks don't realize just how limited their competency is, and how unforgiving the diving environment can be. That's a legit concern.

Richard.

 

[xyrandomyx]

A Quick Contingency "Rock Bottom" Calculation and Gas Plan Estimate for Open Water for a deep dive to 30 meters to illustrate why beginners/novices should NOT be going to these depths beyond 18 meters:

For a single 11 litre tank (AL80), a total of 11 litres/bar metric tank rating and a diver's volume Surface Consumption Rate (SCR) of 22 litres/min -same as a pressure SCR of 2 bar/min*ATA (divide 22 litres/min by 11 litres/bar)- using an example NDL air dive to 30m (4 ATA) depth in Open Water.

Emergency Reserve/Rock Bottom pressure calculation, from 30 meters with one minute stops every 3 meters to the surface,
-->Just "tally the ATA's":
4.0
3.7
3.4
3.1
2.8
2.5
2.2
1.9
1.6
1.3


Sum Total: 26.5


Multiplied by 2 bar/min*ATA equals 53 bar Rock Bottom absolute reading remaining on your SPG. --this also happens to be the pressure in bar needed for one person in an emergency contingency to reach the surface with the above minimum decompression ascent profile.

So ideally for a two person buddy team, multiply 53 by 2 which is 106 bar for both to reach the surface (sharing in a buddy Out-ot-Gas contingency).

But realistically, for two experienced divers stressed: 106 bar plus 30% of 106 bar equals 138 bar Rock Bottom SPG reading.

For two novice divers stressed: 106 bar plus 100% of 106 bar equals 212 bar (200 bar is the standard starting pressure for a full AL80/11L Tank!!!)
--->obviously then, two novice divers on single 11L tanks should not be diving to 30m for any significant length of time. . .

Sorry, this is a bit off-topic (as my posts often are), but -- why 'one minute stops every 3 meters'? I would've used one or two minutes at maximum depth (to allow for resolving or attempting to resolve issues) followed by a direct ascent at 9 metres per minute, plus a safety stop for 3 minutes at 6.5 metres.

 

[Kevrumbo]

A Quick Contingency "Rock Bottom" Calculation and Gas Plan Estimate for Open Water for a deep dive to 30 meters to illustrate why beginners/novices should NOT be going to these depths beyond 18 meters:

For a single 11 litre tank (AL80), a total of 11 litres/bar metric tank rating and a diver's volume Surface Consumption Rate (SCR) of 22 litres/min -same as a pressure SCR of 2 bar/min*ATA (divide 22 litres/min by 11 litres/bar)- using an example NDL air dive to 30m (4 ATA) depth in Open Water.

Emergency Reserve/Rock Bottom pressure calculation, from 30 meters with one minute stops every 3 meters to the surface,
-->Just "tally the ATA's":
4.0
3.7
3.4
3.1
2.8
2.5
2.2
1.9
1.6
1.3


Sum Total: 26.5


Multiplied by 2 bar/min*ATA equals 53 bar Rock Bottom absolute reading remaining on your SPG. --this also happens to be the pressure in bar needed for one person in an emergency contingency to reach the surface with the above minimum decompression ascent profile.

So ideally for a two person buddy team, multiply 53 by 2 which is 106 bar for both to reach the surface (sharing in a buddy Out-ot-Gas contingency).

But realistically, for two experienced divers stressed: 106 bar plus 30% of 106 bar equals 138 bar Rock Bottom SPG reading.

For two novice divers stressed: 106 bar plus 100% of 106 bar equals 212 bar (200 bar is the standard starting pressure for a full AL80/11L Tank!!!)
--->obviously then, two novice divers on single 11L tanks should not be diving to 30m for any significant length of time. . .

Sorry, this is a bit off-topic (as my posts often are), but -- why 'one minute stops every 3 meters'? I would've used one or two minutes at maximum depth (to allow for resolving or attempting to resolve issues) followed by a direct ascent at 9 metres per minute, plus a safety stop for 3 minutes at 6.5 metres.

The above contingency profile incorporates a relatively sane & controlled ascent technique --essentially 30 seconds pause at each 3 meter (or 10 foot) interval, with a 30 second moving ascent time in between-- so you & your air sharing buddy don't both shoot to the surface together like a Submarine-Launched-Ballistic-Missile. . .

The main point of the gas planning exercise above is that two novice divers gas sharing in an emergency Out-of-Air Contingency from a single 11L/AL80 Tank may not have enough breathing gas to reach the surface from 30 meters/100 feet deep --which is why beginning/novice divers should not be diving any deeper than 18m/60' for any significant length of time.

 

[DevonDiver]

I just associate added depth with added risk,....

That'd be a fair association to make.

From the simple perspective of 'time to the surface', you are safer in shallower water than deeper. The recommendation to remain above 18m/60ft keeps you within 1 minute of the surface (at a max ascent rate of 18m/60ft per min). Most people can manage 1 minute without air to breathe, if their life depended upon it. Less people would be confident of 2+ minutes without an inhalation.

Add to that the issues of nitrogen absorption and the threat of DCS. Shallow-water dives keep your nitrogen uptake lower... reducing risk to the diver in the event that they ascend to quickly - whether 'forced to' by some emergency they can't deal with at depth or because of buoyancy issues leading to a rapid, uncontrolled ascent.

Another consideration is nitrogen narcosis. Whilst not a physiological danger in itself at recreational depths, it does increase the risk of the diver making mistakes. It can be a recipe for disaster when combined with shorter no-deco times (DCS issues), faster air consumption at depth (air depletion issues) and less ingrained confidence (anxiety/panic issues). Most divers won't "feel" the effects of narcosis above 30m/100ft, but those effects can be very insidious - diminishing mental capacity without any obvious signs or symptoms.

As divers progress onto deeper dives, the sum of these combined issues exceeds the threat caused by the issues viewed in isolation from each other.

that's why I wondered if there was a mid-level course rather than the deep diving course that seems to be ~130ft (no where near my ability or comfort to participate in extended learning at the moment).

There's a plethora of courses available that can increase your knowledge, skill and confidence that aren't focused upon the depth alone. You could dive for the rest of your life without exceeding 18m/60ft...and still progress your training effectively and regularly. Avoid having a fixation on depth as the solitary barrier to diving development..

Within the PADI system, you have courses that develop buoyancy (PPB) and navigation skills. There are courses that provide competency on new equipment, such as sidemount, dive propulsion vehicle or drysuit. There are courses that introduce new activities, such as photography or videography. There are also courses that train you for new diving environments, like cavern, wreck or ice. Outside of PADI, you have some excellent courses like the GUE 'Fundamentals'.

A good instructor, can use any of those courses to develop your overall diving competency and confidence. None of those courses need influence your decision to limit/slowly progress your diving depth.

One thing that does make me scratch my head is dive tables in that if PADI recommends 60ft max depth, and if air becomes toxic past ~100ft, why include the dive tables up to 140ft?

Others have enlightened you on this - air does not become toxic at such depths. The issue of narcosis (not a toxic effect) is very real, but not very dramatic, above 30m/100ft. It can be more pronounced between 30m/100ft and 40m/130ft however. Ingrained dive skills and refined situational awareness do a lot to counter the issue of narcosis within recreational diving depths - which is why experience and training have a direct link with dive depths.

Another issue (that is related to deco theory) is your no-decompression limit. If you look at the tables your max NDL for 40m/130ft is very short (~4-5 min). Would there really be any point in the tables showing deeper depths, when the diver themselves is limited to no-deco diving? Anything less than ~4-5 min would fail to provide a meaningful dive, especially if/when descent is factored into the bottom time. PADI, as do most agencies, recommend against completing 'bounce dives' (very short duration deep dives).

Given I want to learn more about this are there any trusted resources regarding decompression theory/ safety and help for gas management?

Read 'Deco For Divers' by Mark Powell. It is an excellent book...and very readable without prior expert knowledge or a background in advanced mathematics...

 

[261311]

Read 'Deco For Divers' by Mark Powell. It is an excellent book...and very readable without prior expert knowledge or a background in advanced mathematics...

Sounds like it's right up my alley, hah- thanks all