Now it's time to choose a wrist computer.

[SaltyCracker]

Nobody in their right mind is going to answer that. The best you can hope is "I personally would set it to 0 but that's just me; what you do is up to you".

I've been told over and over that "it's up to me" in several different ways. That much has been obvious right along. And I never really have been asking for absolutes or for somebody to tell me what to do anyway.

Which is better: the model that results in clinical DCS on every 1000th dive, every time, day in, day out, or the model that has 1 in 1100 chance of DCS but may have you do 2200 dives just fine and bend you back-to-back on your 2201st and 2202nd ones? This is covered in first chapters of the original DSAT report, their work was aimed at reliable and consistent. SAUL's predictions, OTOH, are just the numbers game and have never been tested or verified as far as I know.

My brain hurts too much to ponder your rhetorical question.
I know that I have a lot to learn and will do the reading/studying required on my own. But I'm just asking questions after-all.
I do want to read the DSAT report though. I looked around and saw reference to it but not the report itself. It looks like it's titled Development And Validation Of No Stop Decompression Procedures For Recreational Diving. Does anyone know where I can find it?

​

 

[SaltyCracker]

Any of the Seac conservatism settings would seem to be conservative enough for most people. L2 or L3 would seem to be good starting points. I normally dive with my computer in 40/85, and that’s been good for me, so I wouldn’t be opposed to L0, but that is ultimately up to you. My daughters also dive, and use Oceanics. I set their computers to use PZ+ instead of DSAT as it’s a bit more conservative.

Running in Dive Planner mode is not a bad idea. Get an idea of what kind of NDL times you are looking at. Also, keep in mind that, regardless of the conservatism settings, you don’t need to hit the NDL on each dive. And, I’m betting that in most cases, you won’t be able to. Most new (adult) divers will be limited by gas supply more than NDL. Kids, on the other hand don’t tend to use nearly as much gas, so your son’s dives may be limited by your gas consumption.

I’d say pick one setting and try it out. Do some dives and see where you are. If you are gas limited, no reason to go for a more liberal setting. If you are hitting the NDL before using up the gas, then maybe bump it one step more liberal. Make notes of how you feel post dive, and make adjustments as appropriate.

Ultimately, that’s the beauty of GFs, you can adjust to where you are personally comfortable. While your computer doesn’t give the true flexibility of some, it’s more than most. 6 presets is not bad at all, most other computers only offer 2 or 3. And remember, even at the most liberal setting on your computer, you are still not at the theoretical max of the algorithm.

Thank you for your opinion. And great point on me more likely being limited by gas supply anyway.
For me, this has been mostly academic. When I used to dive long ago, I never did learn the finer points of what my computer was telling me or really understand my limitations. I've found some good articles on these subjects and will read up before asking more questions for now.

 

[dmaziuk]

I do want to read the DSAT report though. I looked around and saw reference to it but not the report itself. It looks like it's titled [/FONT][/SIZE]Development And Validation Of No Stop Decompression Procedures For Recreational Diving. Does anyone know where I can find it?

​

Rubicon Foundation, normally, but they're down with no ETA for re-appearance. (@tbone1004 might know something?) I have a copy at home but I won't get there until next year. If planes are still flying then and all that. PS. there's a couple of "academic" leechers like researchgate that claim they have it, if you have an affiliation with academentia you may be able to get it there.

 

[scubadada]

...I do want to read the DSAT report though. I looked around and saw reference to it but not the report itself. It looks like it's titled Development And Validation Of No Stop Decompression Procedures For Recreational Diving. Does anyone know where I can find it?

​

I have a PDF of the report but I can't upload it to SB

Send me your email address by direct message and I will send the report to you. If anyone else wants it, do the same.

 

[Dan]

Funny.

I thought that at Cocos they pull you out of the water that fast so that the tiger shark doesn't chew your *ss off

Tiger Sharks are sneaky. You need to keep your eyes on a swivel


…and when one coming towards you, keep your eyes on it 100%, otherwise….

 

[SaltyCracker]

If planes are still flying then and all that.

Sounds like Dec 31st 1999.

...if you have an affiliation with academentia you may be able to get it there.

 

[dmaziuk]

Tiger Sharks are sneaky. You need to keep your eyes on a swivel

…and when one coming towards you, keep your eyes on it 100%, otherwise….

Otherwise keep feeding them until they learn to associate humans with food. What could possibly go wrong.

 

[Belzelbub]

Thank you for your opinion. And great point on me more likely being limited by gas supply anyway.
For me, this has been mostly academic. When I used to dive long ago, I never did learn the finer points of what my computer was telling me or really understand my limitations. I've found some good articles on these subjects and will read up before asking more questions for now.

I totally understand the academic aspect, and definitely respect it. I can relate. I did lots of research before I got my computers and am definitely interested in how it all works.

To give you a feel for how the different algorithms or settings can behave, here's an example. This was the same dive done with an Oceanic VT4.1 running DSAT. This was a training dive, and there was an incident with another diver who happened to be who I was buddied with. I was looking into this dive trying to see if there was anything in the profile that could have contributed to the incident. We were diving the same gas, and had roughly the same profile. Incident was apparent around 85' in depth. Turned out to be IPE, so not really anything that the dive parameters themselves influenced. She's made a full recovery, and is still diving.

First screen shot is from DiverLog, the next two are from Subsurface. Diverlog uses the computer's algorithm. Subsurface just uses the data from the computer and calculates NDL, ceilings, etc. using Buhlmann (or VPM) with the GFs you choose (or conservatism in the case of VPM).

The DiverLog image shows the point I selected for each example (vertical black line), with Subsurface, I just pointed the cursor at the same point, but it is missing from the image. NDL varied as expected based on the algorithm/settings.

DSAT showed 17 minutes remaining (NDC Time).

ZHL 40/85 showed 7 minutes. (NDL)

ZHL 60/60 (Seac L5) indicated that this was a deco dive as at that point, I had a ceiling of around 10'. Since it was light, it actually cleared on the way up, so I wouldn't have needed to make the stop.

 

[drk5036]

I think @scubadada ‘s posts here have hit a really good point, and it’s why I always recommend shearwater computers. More data is always better, and let’s us make better decisions.

A question i am very interested in, or pose as a thought experiment is, who is safer, the diver using a GF high of 95 or 75, if you end the dive with a SurfGF of 55? I think both are equally safe.

If you are diving with a GF high if 70, and your divemaster is using DSAT, you are either going to go into “deco” by following, or call the dive early. I had this happen when I was in Okinawa. I was using GF high of 85. We did a dive where we popped down to 35 meters to check something out in about 10 minutes, then spent the next 10 minutes at around 25 meters. By this point I was riding the NDL and might have even gone into “deco” with my surfGF right around 85. However, we then spent the next 18 minute between 10 and 7 meters, meaning I ended the dove with a surf GF around 55.

If you do a dive the way most guided dives are run (on a reef at least), you will start deep then end the dive very shallow. If I was using a conservative computer, I would have probably accrued some “real” deco time on this type of dive, but given how low my final surfGF was, any deco time would have cleared long before I needed to surface.

For the type of diving I’m doing, which is similar to most recreational divers, using a “conservative” setting isn’t going to change the results of my dives at all. It’s only going to send me a “false alarm” when in reality I’m not close to going over the limit. The only way in which this actually provides some level of increased safety is in the case of some kind of incident, where I need to abort the dive immediately. In that case, my computer not allowing me to reach a surfGF of 80 means I would reach the surface in an emergency with a lower nitrogen load.

If anyone sees any errors in my thought process id be happy to think about it further.

 

[KenGordon]

I've been told over and over that "it's up to me" in several different ways. That much has been obvious right along. And I never really have been asking for absolutes or for somebody to tell me what to do anyway.

The trouble is that you are not really in a position to make an informed choice. All you have to go on is the various opinions of faceless people on the internet. The majority of those opinions are based on fashion, hearsay and guessing based on observed behaviour of computers.

In diving it is very hard for people to figure out what they should really do, especially in the face of “professionals”. Don’t get bent because a guide tells you to surface, but do listen to the briefings so you know why you might be being told to surface. Missing lunch vs getting your leg bitten…

For relatively shallow no stop dives I use the equivalent of your L0, maybe L1 if a long way from a chamber. For half serious deco dives I use an equivalent to L1.

ZHL 40/85 showed 7 minutes. (NDL)

Can you set subsurface to 85/85 and do it again?