Do not ever say you are a rescue diver

[boriss]

I have never seen a dive operation anywhere in the world that limits OW certified divers to 60 feet. A small percentage of dive operations will limit dives in the 100 foot range to people with AOW, but the vast majority do not. I have never seen a dive operation anywhere in the world that requires the Deep Dive specialty for dives deeper than 100 feet.

Was this a typo? You definitely can't go on an "advanced" dive without advanced certification, etc. Maybe I'm just not understanding your point?

I present that possibly; 40 meters rounds (for practical purposes) to 130 feet and 5ATA. Makes it pretty simple as a base to say they are equal. Now if I was to ride the NDL ((no decompression limit)(no deco limit)) to the limit of most models these values would be different and would involve some decimal values. who wants to remember that. Regardless of where in the world I am diving we can all understand that if one says the recreational dive is 40 meters, I can equate that to 130 feet, or if someone says 5ATA, I know that is the same as 40 meters or 130 feet. These us basically equal values and a little cushion on time to going into deco (decompression).

There's a difference between doing algebra and understanding the physiological effects of these recommendations, however. When it comes to laws, rules or mere suggestions they're typically an approximate line drawn in the sand in the name of some greater good. In Scuba that greater good is safety.

For example, it's recommended that we target a PPO2 of 1.4 for the work portion of the dive and 1.6 for deco, but are you going to convulse and die if you are at 1.5 for the working portion of the dive? Probably not. The problem is we don't know what the limits are for any specific diver at any given time. We aren't robots. The MOD @ 1.4 of Air is 187, however the world record is 452ft. That's a PPO2 of 3.1! Just because a handful of people can tolerate that for a small period of time doesn't mean the majority can.

Lots of these recommendations are just that and they have a pretty decent buffer, because there's no need to flirt with danger for the average person. People don't go from 40m to 41m and die, but an arbitrary line had to be set and there it is.

OW is 20m
AOW is 30m
Deep is 40m
Technical >40m

Nice simple round numbers

 

[Belzelbub]

Now I know I'm from the south and I might be a little slow but in all my discussion and use of the words decompression or deco when describing a dive, mean or describe the same thing, deco is just an abbreviation the word decompression. I can't remember a time when this has confused someone.

The example I will use "I am going to be making decompression stops on this dive." "I am going to making deco stops on this dive." "my decompression limit on this dive is 20 minutes" "my deco limit on this dive is 20 minutes"

Deco vs. Decompression is not the main point that some are having problems with. It is what is meant by a ”deco dive” or “decompression dive”. Not that there is a difference between the two.

There are some that want to argue that every dive is a decompression dive since every dive involves decompression. While it is technically correct that all dives do involve decompression in some sense, a 30 minute dive to 30 fsw is not what most people would call a deco dive or a decompression dive.

The generally accepted definition of a deco dive is one where the absorbed N2 in a divers tissue is high enough that a direct ascent to the surface is not expected to release enough nitrogen where the dive would be considered safe from DCS. Therefore, the dive parameters would require one or more stops along the way to allow the N2 to offgas such that large bubbles are not expected to form. The inclusion of the decompression stops, though not a safety stop, is what most divers would understand when the term deco dive is used.

 

[Belzelbub]

OW is 20m
AOW is 30m
Deep is 40m
Technical >40m

Nice simple round numbers

These are training limits not certification limits. An OW diver is not limited (by their certification) to 20M. Some dive ops may require additional training of some sort beyond OW, but that is the op’s policy. It does not mean that the certifying agency puts that limit on divers.

Training limit just means that the dives during the course should not exceed those depths. Now, the dive agencies do seem to do a good job of creating the impression that OW has a “limit” of 60’/20M. That’s good for business as they sell training material, so if there is an understanding that there is a limit that requires additional training, that’s helps them to sell additional certs.

Oh, and the AOW training limit is not so cut and dried. Several of the training dives I did prior to getting the card that says AOW were in excess of 100’. That’s because I took a Deep specialty. I didn’t take an AOW course. With that, and my 3 other specialties, I got an AOW recognition card.

 

[tursiops]

Several of the training dives I did prior to getting the card that says AOW were in excess of 100’. That’s because I took a Deep specialty. I didn’t take an AOW course. With that, and my 3 other specialties, I got an AOW recognition card.

This sounds against PADI standards, since a prerequisite for Deep is Adventure Diver. did you have that as a prereq?

 

[boulderjohn]

Was this a typo? You definitely can't go on an "advanced" dive without advanced certification, etc. Maybe I'm just not understanding your point?

Why not?

Some operators will require AOW for dives in the 100 foot range, but it is only a small percentage that do, which is indicated by the humor in this clip:

 

[Beau Holden]

Lots of these recommendations are just that and they have a pretty decent buffer, because there's no need to flirt with danger for the average person. People don't go from 40m to 41m and die, but an arbitrary line had to be set and there it is.

OW is 20m
AOW is 30m
Deep is 40m
Technical >40m

Nice simple round number

Agreed

 

[boriss]

Deco vs. Decompression is not the main point that some are having problems with. It is what is meant by a ”deco dive” or “decompression dive”. Not that there is a difference between the two.

There are some that want to argue that every dive is a decompression dive since every dive involves decompression. While it is technically correct that all dives do involve decompression in some sense, a 30 minute dive to 30 fsw is not what most people would call a deco dive or a decompression dive.

The generally accepted definition of a deco dive is one where the absorbed N2 in a divers tissue is high enough that a direct ascent to the surface is not expected to release enough nitrogen where the dive would be considered safe from DCS. Therefore, the dive parameters would require one or more stops along the way to allow the N2 to offgas such that large bubbles are not expected to form. The inclusion of the decompression stops, though not a safety stop, is what most divers would understand when the term deco dive is used.

Again, it's all about context. They're all "decompression dives," however at some point we draw a line in the sand and say that past this point we have mandatory decompression. You have to ask yourself: what determines that? It's a table or an algorithm.

Prior to taking AN/DP, I'd practice deco diving by having one computer set to a more conservative GF. According to one computer this was a "decompression dive" and according to another it was an NDL dive. Just like my previous post above about lines being drawn in the sand, this is another one. We plan around certain parameters and those parameters determine the type of decompression that's required/recommended.

Again, I'm not trying to be difficult, I know we need to differentiate, but that differentiation is based on context. It's murky near the line and very easy to define in extremes.

 

[Belzelbub]

This sounds against PADI standards, since a prerequisite for Deep is Adventure Diver. did you have that as a prereq?

It quite possibly could be against PADI standards. That’s OK though, as the instructor I used is not a PADI instructor. It’s allowed under SSI standards.

The post I was commenting on didn’t specify PADI. Just AOW. I thought the inclusion of AOW as recognition after 4 specialties would have hinted enough that I wasn’t talking PADI.

 

[Belzelbub]

Again, I'm not trying to be difficult, I know we need to differentiate, but that differentiation is based on context. It's murky near the line and very easy to define in extremes.

I almost wrote something to include that gray area, but decided it wasn’t critical. There is a line at some point, and you are correct that it will vary based on the algorithm and conservatism settings or table used. With each, there is a line that when crossed means a stop on the way up is warranted.

Point is that asking a group of divers what a deco dive is will likely result in the majority of divers agreeing that it means a stop is needed on the way up. If using a computer, it can be a bit murkier as the obligation may clear on the way up to the stop depth.

 

[brsnow]

I have never seen a dive operation anywhere in the world that limits OW certified divers to 60 feet. A small percentage of dive operations will limit dives in the 100 foot range to people with AOW, but the vast majority do not. I have never seen a dive operation anywhere in the world that requires the Deep Dive specialty for dives deeper than 100 feet.

You will see this much more readily in the area of overhead environments. When I debated with PADI headquarters about their statements in this regard (and thus got some of that language changed), I pointed out that the current PADI language prohibited any overhead environment to anyone without proper certification for overhead environments, and yet every operation in the world allows customers to go inside wrecks or go through coral swim throughs or lava tubes.

The dive operation's insurance is indeed the primary determiner of such policies.

I stayed at Blue Angel in Cozumel a couple of weeks ago and they did keep a 60 foot max depth. Having been going to Cozumel regularly since 2009, this is the first I have run into it there or actually anywhere I have dove. I did not dive with them the rest of the trip but my dive buddy did one more time and they kept the 60 foot max on that trip as well. So it does exist.