No Deco rules - Local Island Diving - Maldives

[Heat Miser]

To give us an idea about the overall profile, what were the average depths? I would imagine they were generally no deeper than 15-20 m (50-65 ft) or many of the divers would have exceeded NDL on some of the dives.

NDL Dive GF 45/95 total run time 38 min (add on 3 min safety stop)

Dive GF 50/70 (same Bottom time, more deco) total run time 49 min

 

[Heat Miser]

I typically dive 3 dives a day with conservative settings of -2 on my Suunto Eon Core and I’ve never had a problem in last 75 dives or so with it. But that’s for the strictly recreational dives - when I learn deco diving next year I plan to keep it strictly at 0 default until I figure I need to be more conservative or not. Not inclined to test the algorithm liberally for deco dives even in theory the way I think about it right now.

If you are going to start diving deco, flick the Suunto and get something running the Bühlmann ZHL-16C dive algorithm. (i.e. Garmin. Shearwater).

The only way you can have a somewhat sensible conversation with your buddy, about dive profile, is if you are running the same algorithm.

Most of the work in deco diving is around the gas planning and runtime management, very hard to do if you cant agree total runtimes.

 

[Heat Miser]

I subesequently downloaded a PADI dive table and I think @boulderjohn is right, There is a very low risk of DCS on the low conservative setting on GARMIN, assuming your doing no deco diving and max depths above 30 meters.

My analogy should be the locals are doing 14-16 MPH in a 15 MPH zone, I'm doing 12 MPH.

Regards

​

 

[Jai Bar]

The Maldives have some local recreational diving regulations (https://archive.tourism.gov.mv/downloads/Divingregulations2003.pdf) restrictions for 30m depth, no deco etc. are probably because they wnat to avoid as much as possible divers getting DCS, knowing the vast distances between diving areas and deco chamber it seems reasonable.

If by "local divers" you mean dive guides who do 3-4 dives on a daily basis, then in most operations that I've been they usually plan the dive so that they don't stay at 30m until the last second of NDL time, they try to gradually multilevel the dive to shallower depths, unless it is a very special dive site such as some chanel with hoardes of sharks. The guests usually have higher gas consumption rate so in many cases they are the ones limiting the bottom time.

In some places I've seen guides asking guests no more than 45 minute dives. One hour is reasonable for a diving safari, for example, as they have to move between sites etc. if some guests would stay in water for 1.5-2 hours it can impact the time schedule, is more task load for the crew, guides and so on.

 

[gmerick]

Monday's boat dive has me rethinking guided dives. My computer is set for gf85. I usually dive unguided, and solo, I keep a close watch on time, depth, gas remaining, and NDL. So, on Monday we were guided on a recreational dive moderately deep. initial descent was to 65 ft, then proceeded down the slope maxing out at 115 for about 5 minutes, then continuing around. everyone seemed to be blissfully happy following the guide, but my low NDL numbers were blinking. I let them get down to 1, and decided I really needed to take care of me. As no buddys were agreed to before the dive (6 divers, a couple, a father/son pair, and two loners). As the other loner had already signaled 1000psi, I joined him above the group. Vis was great, and I had a better appreciation of the site from 25 feet up. As the main group started their ascent, we two loners went to safety stop depth, and I let my 5 min (adaptive) timer expire, then signaled going to the boat.
After the dive, I asked our guide if maybe my computer was misleading me, the guide casually said no, she was several minutes into DECO, but just did a "slow ascent". Comparing with two other experienced divers, they were into DECO. The two loners may have been the only ones within NDL, him because of low air, and I had been watching my limits.
This is not a normal occurrence, but I have seen it in maybe 5-10% of guided dives - most all on the first dive of the day.

 

[Heat Miser]

Monday's boat dive has me rethinking guided dives.

In my view the guides should stay with the diver.

I have had a few that didn't want to push the depth I wanted (on a second open circuit Nitrox dive) and stay a bit higher, but its fair to say they were allways within 5-8m (15-20 feet of me).

Since posting this I have modified only my No Deco dive gradient factors and now dive 40/85, for a typical 30 meter dive, < 1 hour with no deco, with gradual ascents. I pretty much exclsuively dive Nitrox, (unless only Air is available, an then I will try to find a different provider)

However it is very diifernt GF for a deco dive, and having had the O-Dive gizmo attached to me previously, use much more conservative settings for deeper deco dives and I ask my buddies to agree to the settings, prior to the dive.

 

[Miyaru]

Look I don’t get the 30m rule at all. If you qualified to do 40 why restrict to 30? Many of the dives are above 30 min so u just b#£hit everyone by marking 30m on dive sheet. I can think of kandooma Thila generally 32-35, kuda Giri over 30m andd fuvamalsh..weeeell

Before this rule became a law, all incidents and accidents with a bad outcome turned out to be all below 30m. Which is why all recreational diving below 30m was prohibited by law. The nice thing about this being a law, is that there's no need for discussion in any Maldivian divecenter about depth.

I know two doctors who did a stint in Bandos, running the recompression facility. Most boring job ever.

Monday's boat dive has me rethinking guided dives. My computer is set for gf85. I usually dive unguided, and solo, I keep a close watch on time, depth, gas remaining, and NDL. So, on Monday we were guided on a recreational dive moderately deep. initial descent was to 65 ft, then proceeded down the slope maxing out at 115 for about 5 minutes, then continuing around. everyone seemed to be blissfully happy following the guide, but my low NDL numbers were blinking. I let them get down to 1, and decided I really needed to take care of me. As no buddys were agreed to before the dive (6 divers, a couple, a father/son pair, and two loners). As the other loner had already signaled 1000psi, I joined him above the group. Vis was great, and I had a better appreciation of the site from 25 feet up. As the main group started their ascent, we two loners went to safety stop depth, and I let my 5 min (adaptive) timer expire, then signaled going to the boat.
After the dive, I asked our guide if maybe my computer was misleading me, the guide casually said no, she was several minutes into DECO, but just did a "slow ascent". Comparing with two other experienced divers, they were into DECO. The two loners may have been the only ones within NDL, him because of low air, and I had been watching my limits.
This is not a normal occurrence, but I have seen it in maybe 5-10% of guided dives - most all on the first dive of the day.

What are "low NDL numbers" ?
Why do you write deco in capitals?

I let them get down to 1

Diving the limits of your computer(s), actually diving the limits of your computer's settings, might look like a clear line between no-stop diving and decompression obligations. But that's just your computer, not for your body. If you want to dive the limits, learn about the grey area where this theoretical limit runs through.

 

[Jai Bar]

What are "low NDL numbers" ?
Why do you write deco in capitals?

For a recreational diver, since NDL means No Decompression Limit (unit is minutes) then, well, NDL = 0 would be the limit.

Since Decompression theory is somewhat based on empirical basis, and each diver's physiology differs, many of us are taught to add more safety measures and not push to the limit.

When OP mentioned that he felt unease and when remaining NDL time was 1 minute he decided to start his ascent, as many know that depending on depth, time spent and ascent rate one may still be ongassing also during part of the ascent.

I think it is safe to assume that by "low NDL numbers" he means that he is imposing on himself added safety measures by not staying at depth below a certain NDL value. It is personal, some feel okay with NDL = 0, others may prefer to ascend to shallower depths when remaining NDL is 5 or 10 minutes. If I had to guess, for OP remaining time of 5 minutes is low. But it is a guess, and for the discussion it is not important if he really meant, say, 6 or 7 minutes. A diver can always ask his buddy- or guide-- to begin ascent if he is uncomfortable, and I'd expect a good buddy- or guide- to oblige. They can discuss the reason for thst during the surface interval.

DECO in capital letters?? There is an ancient proverb that goes like "The shy does not learn, nor the strict teaches". I apologize if the translation is bad, I am not an English speaker. Anyway, although unlike NDL, DECO is not an abbreviation and technically should be written in full "decompression" everyone uses the short "deco" and even when the OP writes "DECO" I am sure that 100% of divers reading this thread know exactly what he meant. Humanity must have worse problems like people confusing "you're, your, there, their"

 

[Miyaru]

... even when the OP writes "DECO" I am sure that 100% of divers reading this thread know exactly what he meant. Humanity must have worse problems like people confusing "you're, your, there, their"

True. I know what he meant.
Still doesn't answer why he used capitals, and I'm always eager to learn since English isn't my first language either.

I think it is safe to assume that by "low NDL numbers" he means that he is imposing on himself added safety measures by not staying at depth below a certain NDL value.

Nice explanation for "low NDL number". But this was about numbers. I only know 1 NDL, I'd like to learn about the others!

 

[Jai Bar]

Nice explanation for "low NDL number". But this was about numbers. I only know 1 NDL, I'd like to learn about the others!
[/QUOTE]

In the diving tables, there is a single value for any given depth. So if the table covers depths from, say, 0 to 30 meters in 3 meter intervals- the table will have 10 NDL values. Technically less, since at 3, 6 and 9 meters it will be empty.

A computer, unlike the table, constantly updates the mentioned value according to present dive parameters. If the diver makes a complete square dive profile the table and computer will be similar (assuming both were produced with the same algorithm!). Most divers actually do mulitlevel and the computer recalculates the NDL according to actual depth.

Technically, he and most of us refer to the time "remaining to reach No Deco Level". This is also the value that most computers display under "NDL" in the screen- how much time before the dive becomes a decompression one. Ask manufacturers why they write only "NDL" and not "Remaining time before reaching No Decompression Limit". I suspect that it is because of limited screen space but maybe if there were german computer manufacturers they would be more precise