Diver vs DM Responsibilities

[Edward3c]

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I should have mentioned, this is a recreational NDL level vacation diver. I understand not to switch between computer and tables, BUT, what is the rule then at this point? Does the 6 hour / 24 hour rule no longer apply when you go into deco bc you’re using a computer?

There isn’t a single answer to this question.

Each brand of tables has its own de-gas times. When I use BSAC 88 Tables they give 16 hours to clear. The 88 Tables are deco tables, a 30m dive for 30 min bottom time requires 3 min @ 6m, 16 hours later I would be back to Surface Code A.

My Suunto Manual gives 48 hours to completely de-gas. A dive incurring mandatory deco could require the full 48 hours to clear.

 

[MaxBottomtime]

If I'm doing the math right, you can hit the NDL at 70 feet in 40 minutes (on a square profile), according to the PADI table. If you have an SAC of 0.4 (not unreasonable for a female in warm water - I average about 0.45 as a similarly experienced male in warm water), you'll hit that having consumed a bit over 50L of air. At 90 feet, you'll get there in 25 minutes and you've only used 40L. That's only just hitting the NDL, and I don't know how long you have to exceed it to need 20 minutes of deco, but she's still got half her tank left. If she's using a very conservative algorithm, I can see it happening. Even more so if she's using a high capacity tank.

It depends on how long she remained at depth, but I have made over 200 dives below 160 feet in doubles without having to make twenty minutes of deco. I'm guessing her DM took her up shallow and then waited there for twenty minutes until the rest of the divers ascended.

 

[KatieMac]

I would guess she had between 80 and 100 dives lifetime.

Am I missing something here? I have less than 40 dives and it would never occur to me to simply ignore my limits and not inform the DM - especially as a new diver. I agree with @outofofficebrb, there must be more to this story.

 

[ratjn]

A POSSIBILITY is the computer was set on very conservative settings. I did a dive once with a backup Suunto Gekko set on maximum levels of conservatism. I was shocked at how quickly this computer was in deco and how long the deco obligation was.

Re-enforced to me the importance of properly setting and understanding the computers I am diving with.

 

[boulderjohn]

I don't think it is the job of the DM to be anything more than a guide; it is the diver's personal responsibility to monitor their own gas and NDL and nobody else's.

I think of the DM as primarily a guide.

A DM's job is to follow the expectations of his or her employer. We have had countless numbers of these threads, and in some cases, dive operation owners participate. In every case I can remember, the operation's owner has said he or she expects the DMs to feel and act responsible for the safety of the divers.

I don’t know I’m a little skeptical if she truly incurred a 20 minute deco obligation on the first dive? How deep for how long and for typical vacation diving with an 80 cu ft single cylinder did she have enough gas to first incure the obligation and second complete a 20 minute stop.

and I don't know how long you have to exceed it to need 20 minutes of deco,

I find it hard to believe that anyone using an AL 80 can get 20 minutes of deco before running out of air during the dive, let alone having enough gas to do the deco.

The one exception would be if the person had a Suunto (or similar computer) with all the settings at the most conservative. I once used a Suunto Cobra (air integrated) as an air pressure indicator only, using a wrist computer to guide the actual dive. During a dive (the second of the day) I realized that the last time I had used the Cobra as a computer had been in Colorado, and i was now at sea level. I still had the setting set for high altitude, and, sure enough, it had me in deco while I still had plenty of NDL time left on the wrist computer. If she had a Suunto with the personal settings AND the altitude settings both at the max, the computer probably would have put her into deco while she was doing a giant stride entry. With those settings, the computer does not want you getting out of bed.

 

[mcohen1021]

I love the thought you guys have put into this topic….

So, knowing the divers and DMs they were using (please do not ask who/where), I know they use standard 3000 psi 80s.

Here’s a little more info regarding scuba day 2:

“94 ft first dive for 54 minutes. Five of us went to deco on that dive bc [DM] wanted us to see something. Second dive 64’, [DM] had us go look at three massive lobster which I feel put me into deco”

I think it would be smart for these private guides to put some policy in so no one get’s mad when a diver is cut off.

Example: If you have ever dove the MV Fling @ Texas Flower Gardens, they have a very strict safety code:

1. 1 alcoholic drink, you’re done diving for the day
2. 1 alcoholic drink after midnight, you’re done diving for that day too
3. Surpass 130 ft on 1st dive, you’re done for the day
4. Surpass 100 ft on 2st dive, you’re done for the day
5. Deco: Done for 24 hours
6. Out of Air: (I think you sit out 1 dive or rest of day)

 

[MaxBottomtime]

I would make #6 done for the trip. There is no excuse for running OOA.

 

[RhodeDiver]

The DM might have been wrong about making you stay down to see something, but at the end of the day you are responsible for your own well being.

If it were me and I was going to go into deco I would simply go up. As they say anyone can call a dive for any reason. Always put your safety and the safety of your loved ones first.

 

[Edward3c]

...
Here’s a little more info regarding scuba day 2:

“94 ft first dive for 54 minutes. Five of us went to deco on that dive bc [DM] wanted us to see something. Second dive 64’, [DM] had us go look at three massive lobster which I feel put me into deco”
...

The dive profiles, as stated, are so far outside tables they can’t be calculated.

It would be more useful knowing the average depth of the dives. In addition what was the surface interval.

Its easy to do 60 minutes on a 30m dive if most of the time is spent above 15m.

 

[outofofficebrb]

I love the thought you guys have put into this topic….

So, knowing the divers and DMs they were using (please do not ask who/where), I know they use standard 3000 psi 80s.

Here’s a little more info regarding scuba day 2:

“94 ft first dive for 54 minutes. Five of us went to deco on that dive bc [DM] wanted us to see something. Second dive 64’, [DM] had us go look at three massive lobster which I feel put me into deco”

It is on the individual diver to look at their NDL and *tap tap tap computer* then signal the time remaining. If the DM does not understand, go to the DM and show them and then signal that you are going to go up a little bit. If NDL was fine at the start of this adventure to see something, it is also the responsibility of the diver to keep eye on the NDL and let the DM know when it's time to go up slightly due to NDL.

I have seen DMs request air levels to ensure people don't run out of air and as a gentle reminder to check air. Asking for NDL is not standard in my experience. A lot of my diving is international in various locations so I have a bit of a sample set. Again, I think it's on the diver to keep an eye on air and NDL either way.