Info Why are tables not taught in OW classes anymore?

[scubadada]

Is a 14min dive to 30m a deco dive or an NDL dive?

Using SubSurface with arbitrary settings and GF high = 95% : 2 min NDL remaining
using GF low = 50%, GF high = 60% : 7min of DECO REQUIRED (ceiling begins 8min into the dive)

so which is it? Deco or NDL?

Personally, I would use the Shearwater presets as a guideline, with a GF high of 95 being liberal, 85 moderate or middle of the road, and 75 as conservative. It is always possible to manipulate an algorithm to make your point.

See the example in a previous post from another thread regarding the probability of DCS following a single dive on 32% at the above GF highs Is there data on how close to NDL undeserved hits occur? From that post, "At a GF high of 75, all the dives at NDL have a risk of <0.001% or 1/100,000." A GF high of 75 is quite conservative, 60 is, well, chosen to make your point clearly.

Using MultiDeco, it looks like 14 min dive to 30 m on air would give you a deco obligation of about 1:30 at 10 ft. So, for your example, diving a GF high of 75 would be a deco dive with a short stop obligation. For most of us, this would easily be a no stop dive. That seems understandable.

 

[boulderjohn]

Is a "deco dive" a dive where decompression occurs? Then all dives are deco dives.

Is a "deco dive" a dive where a stop is done to decompress? Then all dives with a safety stop are deco dives.

Are only dives that have a stop called a deco stop "deco dives"? Planed stops, or executed stops?

What about dives that were not planed to require a "deco stop" that accidentally have a "deco obligation" according to the divers computer settings but the diver didn't notice it, and ascended without a stop and without DCS? No deco stop was planed or executed, is that a "deco dive." What if her buddy that did the identical dive did get DCS, does that make it a "deco dive" for one but not the other?

The term is somewhat fuzzy, and policing the ways it is used is counter productive to communication. Those that say "all dives are deco dives" are communicating a valuable concept to understand about what is actually happening on a dive. Those that say "dives with deco stops are deco dives" are communication valuable ideas about the practical execution of dives.

Like most words and phrases, it has multiple definitions depending on the usage. Take a look in any dictionary, very few words have only one definition listed.

This is is what I object to:

It is not a "misstatement" it is a different "what is commonly called a decompression dive" than the one you use below, but as you note, it is a common statement. It is not a "misstatement". It is completely correct given the definition being use, which is a common (as you state above) definition.

Here you are a little more reasoned, note what I have put in bold:

Please, we just had an entire thread on this.

As a former English teacher, let me explain how language works. We have things called "words," and these words can have a variety of meanings, and we use context to tell us what they mean. Sometimes different words are put together to form what we call "phrases." In certain contexts, phrases can take on the characteristics of a single word because they are commonly understood to function as a single word. For example, in golf, a "tee shot" is the first stroke a golfer takes on a hole. It is often taken with the ball sitting on a tee, but it does not have to be. Golfers understand that if the phrase "tee shot" means the first stroke on a hole, whether or not a tee is used.

We have similar phrases that have taken on meaning in scuba. One of them is "decompression dive." If someone says that they did a decompression dive, almost everyone will understand that the dive that was done included required decompression stop(s). That is because we understand that the phrase has a specific meaning of a specific kind of dive.

Want to know how common that that understanding is? Just Google the phrase "decompression dive" and see how many web sites define a decompression dive as a dive requiring decompression stop(s).

When a phrase has reached that level of common understanding, you cannot take the individual words apart and argue that it should mean something else.

 

[L13]

A GF high of 75 is quite conservative, 60 is, well, chosen to make your point clearly.

I'm fairly certain that @Dr Simon Mitchell mentioned using a GF high of 60% on one of his recent expedition dives, though I might me misremembering it.

But, as you say, with a GF of 75% it still has a deco obligation, so my point is still made.

 

[L13]

Please, we just had an entire thread on this.

As a former English teacher, let me explain how language works. We have things called "words," and these words can have a variety of meanings, and we use context to tell us what they mean. Sometimes different words are put together to form what we call "phrases." In certain contexts, phrases can take on the characteristics of a single word because they are commonly understood to function as a single word. For example, in golf, a "tee shot" is the first stroke a golfer takes on a hole. It is often taken with the ball sitting on a tee, but it does not have to be. Golfers understand that if the phrase "tee shot" means the first stroke on a hole, whether or not a tee is used.

We have similar phrases that have taken on meaning in scuba. One of them is "decompression dive." If someone says that they did a decompression dive, almost everyone will understand that the dive that ass done included required decompression stop(s). That is because we understand that the phrase has a specific meaning of a specific kind of dive.

Want to know how common that that understanding is? Just Google the phrase "decompression dive" and see how many web sites define a decompression dive as a dive requiring decompression stop(s).

When a phrase has reached that level of common understanding, you cannot take the individual words apart and argue that it should mean something else.

Except you said it was a "common" misstatement. Which, since it isn't in fact a misstatement, means that the phrase does in fact have more the one "commonly understood" meaning. As a former English teacher you should know that, just like words, sometimes phrases have more than one common (or even less common but still legitimate) meanings. And the very fact that you describe the alternative meaning as "common" in your own post shows that your recognize this. You just don't like it.

Personally, I think both usages are valuable.

 

[scubadada]

...so my point is still made.

Deco is in the eye of the beholder. You dive a GF high of 75 or use a Cressi computer, you have a deco dive. I dive a GF high of 95 or use an Oceanic computer running DSAT, I easily have a no stop dive.

 

[boulderjohn]

I'm fairly certain that @Dr Simon Mitchell mentioned using a GF high of 60% on one of his recent expedition dives, though I might me misremembering it.

But, as you say, with a GF of 75% it still has a deco obligation, so my point is still made.

Simon in the recent past has used GFs of 50/80.

That does not make any difference in what I said. What happens to your body during the dive is one thing. What you do with a decompression algorithm to keep safe is another.

 

[L13]

For example, in golf, a "tee shot" is the first stroke a golfer takes on a hole. It is often taken with the ball sitting on a tee, but it does not have to be. Golfers understand that if the phrase "tee shot" means the first stroke on a hole, whether or not a tee is used.

I've also heard golfers say they were going to the driving range to practice their "tee shot" even though the shots were not the "first stroke on a hole". Not the primary meaning, but a useful related secondary meaning.

I guess I wouldn't be surprised if they went on a golf board and got told they were wrong to use "tee shot" that way. But the fact of the mater is that may golfers do use it that way, and they aren't "wrong".

 

[boulderjohn]

I'm fairly certain that @Dr Simon Mitchell mentioned using a GF high of 60% on one of his recent expedition dives, though I might me misremembering it..

As long as we are citing Dr. Mitchell, I would like to point out that he is the primary source for what I have been writing in recent posts.

A few years ago I published an article on the current thinking on deep stops for decompression diving. Dr. Mitchell helped me throughout the process, including a careful proofreading of the final draft. When I was done, I wanted to write a similar article for NDL diving. He said he could not help me because NDL diving and decompression diving are different, the research on differing ascents on NDL dives is not clear, and he himself does not have a strong opinion on different levels of safety in different NDL ascent strategies.

Undaunted, I set out to read the research myself, and when I was done researching, I decided that NDL diving and decompression diving are different, the research on differing ascents on NDL dives is not clear, and I do not have a strong opinion on different levels of safety in different NDL ascent strategies. I therefore did not write the article.

But I learned a lot during that research. One of the things I learned is that there really is a difference between NDL dives and decompression dives, which is why I get touchy when people say all dives are decompression dives. Yes, all dives include decompression, but the phrase "decompression dive" has acquired a specific meaning limited to a specific kind of dive.

I cannot imagine that on February 2 each year, in households across America, people hearing newscasters talk about "Groundhog Day" are shouting at the TV sets "No! Groundhogs exist all year long, so every day is groundhog day!"

 

[johndiver999]

Except you said it was a "common" misstatement. Which, since it isn't in fact a misstatement, means that the phrase does in fact have more the one "commonly understood" meaning. As a former English teacher you should know that, just like words, sometimes phrases have more than one common (or even less common but still legitimate) meanings. And the very fact that you describe the alternative meaning as "common" in your own post shows that your recognize this. You just don't like it.

Personally, I think both usages are valuable.

yes yes of course, you think that both uses of the term, which are by their very nature contradictory, are valuable. Someone says "white" and you will argue that white looks black - in the dark. Makes perfect sense and aids tremendously in communication.

To prove my point, I could say, "Joe got bent on a no-deco dive". Everyone (reasonable people anyway) will understand roughly what that means.

 

[tridacna]

I've also heard golfers say they were going to the driving range to practice their "tee shot" even though the shots were not the "first stroke on a hole". Not the primary meaning, but a useful related secondary meaning.

That’s nonsense. No golfer ever says that. You go to the range to practice “driving”, “irons” or “chipping”. You just made that up.