Past NDL. And then this???

[stepfen]

When you're at 25m depth, and your computer tells you to ascend to 3m during 8 minutes, you ascend with approximately 3m/min.

My computer does not tell me to ascent and that's exactly my point. All the computer is doing is to "inform" me ("inform" is the exact word used in the manual) :
- that I am in deco
- time and depth of the deco stop (that's clearly a requirement/mandate)
- and quoting the manual: "TOTAL: indicating the total ascent time" (ascent + deco time + safety stop) . To my understanding this is not a mandate, it is just a piece of very useful information.
It is mentioned nowhere that once in deco I should stop the dive and start a fast ascent to the deco depth.

So, the PADI books don't mention it, my computer's manual doesn't mention it, my instructor didn't mention it (during the class all was mentioned was to stay away from NDL) and I was supposed to know it. Fair enough.

Anyways. Maybe I can't express what I am trying to say clearly enough to be understood.

 

[stepfen]

And to make it clear I don't blame PADI, Cressi or my instructor for the incident. As I repeated several times it's not a blame game from my side. I think it is something important missing from their text and I just highlight it for others to know.

 

[Neilwood]

My computer does not tell me to ascent and that's exactly my point. All the computer is doing is to "inform" me ("inform" is the exact word used in the manual) :
- that I am in deco
- time and depth of the deco stop (that's clearly a requirement/mandate)
- and quoting the manual: "TOTAL: indicating the total ascent time" (ascent + deco time + safety stop) . To my understanding this is not a mandate, it is just a piece of very useful information.
It is mentioned nowhere that once in deco I should stop the dive and start a fast ascent to the deco depth.

So, the PADI books don't mention it, my computer's manual doesn't mention it, my instructor didn't mention it (during the class all was mentioned was to stay away from NDL) and I was supposed to know it. Fair enough.

Anyways. Maybe I can't express what I am trying to say clearly enough to be understood.

Not your fault.

Unfortunately it looks like your instructor missed some pretty useful information and (if the new manuals are as you say - I will have to check mine) the current manuals seem to view diving beyond NDL as something not to be mentioned as possibly too scary for new divers. Gas planning is also something that seems lacking in OW courses (or a large portion of them). A basic 5 minutes would probably allow enough time to cover "emergency deco" procedures with the side note that they should be avoided if possible (my instructor did mention them).

The reason for the ascent is due to the fact that, at depth, deco can accumulate at a fairly scary rate (as you are now aware). If it accumulates to the point at which you no longer have the gas to do the required stops, you end up with the situation of having to make the choice between DCS and drowning (note your buddy might not be carrying enough gas for the two of you for the deco if that wasn't planned for.).

Decompression diving isn't that scary if trained for and planned for. The issue is, as you have found out, what happens if you end up deco diving without planning.

 

[Miyaru]

My computer does not tell me to ascent and that's exactly my point.

That little arrow in the middle pointing upwards and flashing, is telling you to ascend.
Having read the manual, Cressi indeed doesn't tell you how fast you should get to the first stop depth (3m in this example). But then again, the Cressi manual is not a decompression diving course and every manufacturer emphasizes this in their manuals.

It's not about blaming and there's no scuba police writing a ticket the moment you exceed the NDL. I can even understand that stepping over the border is exhilarating and you "always" get away with it........fatalities only happen during the last dive!

Last April, at the end of a dive to a 50m wreck, three divers were riding out a few minutes of deco. They were not trained for a dive deeper than 40m, but then again, nearly everybody visited the wreck with 15 liter single tanks and they were back at the surface after 20 minutes total divetime. Whatever you think of it, it's their own reponsibility.
At least these three people were diving with doubles. They were reluctant to do that same wreck again, so another instructor and I proposed a different approach: plan the dive ahead for every minute, take it with you on a slate and follow the plan. Next day, they all did the dive and followed the plan which was written down on each of their slates.
Their experience afterwards: looking around on the wreck was so much more relaxed, their gas consumption was way below their calculations on the slate, no surprises on the way up with regards to what deco time the computers would display. For them it was a peek into the kitchen of techdiving and they liked it.

Now compare that to the feeling you had during your dive, where your computer kept beeping and displaying an ever increasing deco obligation. I can imagine that your heart rate was higher than normal, looking at your SPG a lot more times than usual. General feeling of discomfort?

 

[Jack Hammer]

He spent 35 minutes hanging at 10 feet and the computer didn't clear. That's insane. I have no idea what algorithm the Cressi Leonardo uses, but it is obviously not an effective tool for any dive involving even minimal deco (unless it can be set in a depth gauge mode to use with a pre-written plan).

I used to dive with a Suunto Gekko. It wouldn't clear deco time unless your were at exactly 20' (6m). If I went up to 21' it beeped like crazy and deco time didn't clear, if I was at 19' it beeped like crazy and time wouldn't clear or was extended by quite a bit. I mainly just used it as a bottom timer, but if i had been following its "deco" it could have been quite confusing. (Totally possible I missed a setting)

 

[Edward3c]

My computer does not tell me to ascent and that's exactly my point. All the computer is doing is to "inform" me ("inform" is the exact word used in the manual) :
- that I am in deco
- time and depth of the deco stop (that's clearly a requirement/mandate)
- and quoting the manual: "TOTAL: indicating the total ascent time" (ascent + deco time + safety stop) . To my understanding this is not a mandate, it is just a piece of very useful information.
It is mentioned nowhere that once in deco I should stop the dive and start a fast ascent to the deco depth.

So, the PADI books don't mention it, my computer's manual doesn't mention it, my instructor didn't mention it (during the class all was mentioned was to stay away from NDL) and I was supposed to know it. Fair enough.

Anyways. Maybe I can't express what I am trying to say clearly enough to be understood.

If your training agency, computer manual or instructor gave you advice on what to do in a NDL situation they could be held liable for having trained you to do that type of diving. Therefore, they don't cover the situation at all. A consequence of a litigation society.

 

[Miyaru]

If your training agency, computer manual or instructor gave you advice on what to do in a NDL situation they could be held liable for having trained you to do that type of diving. Therefore, they don't cover the situation at all. A consequence of a litigation society.

The OP is not diving in the US. In the rest of the world, you won't get sued that easy.....

 

[boulderjohn]

Through the discussion, and thank you all for this, it is now clear. But how the heck was I supposed to know that before the incident? Since it is so vital, shouldn’t it be mentioned clearly in the manuals? Eg In case of emergency deco, call the dive and ascent as soon as possible (<10m/min) to the first deco stop following your computer’s instructions.

A) Once in emergency deco, calling the dive and going up to deco depth FAST is so important step but it is not mentioned anywhere in the manuals, and
B) Cressi (and hence Subsurface) marks any ascent faster than 4m/min as a warning

The standard ascent rate for RGBM is 30 FPM. I just scanned the Leonardo manual and have to admit I could not find it. It is important to note that no one has said you need to ascend FAST. What everyone has said is that you ascended FAR too slowly. You should have ascended at a normal ascent rate.

Here is what your computer manual says about exceeding decompression limits on page 50:

In the event that you have exceeded the no decompression limits, Leonardo will assist with specific information related to surfacing and related decompression information. Upon violating the no decompression limits, the computer will issue a sound alarm, and the display changes as in the figure 22, providing the diver with the following information: 1) Stop icon with the writing DECO, showing that the no decompression limits have been violated and that decompression stops must be performed. The arrow indicating UP flashes. 2) Depth of first decompression stage (the deepest), given in meters (m) or feet (ft.). It may vary from a maximum of 78 ft. to a minimum of 10 ft., by steps of 10 ft.. 3) Time in minutes for the first decompression stage (the deepest). 4) TOTAL icon, indicating the total ascent time, that is the time required to ascend to the deepest stage, respecting the ascent rate, PLUS the stop time at that depth and at any other subsequent stop (including the deep stop if necessary), PLUS the safety stop time, PLUS the time required to reach the surface after completing the decompression stages. 5) “DIVE. T” icon giving the total time spent while diving.​

Actually, it is mentioned in earlier editions of the PADI OW manual.I suspect it was removed in the most recent edition because it was thought to be an unnecessary statement. Apparently not

I have never head the terminology either of you used, and I have been a PADI professional for 17 years now. Here is what it says on the back of my RDP:

If a no decompression limit is exceeded by no more than 5 minutes, an 8-minute decompression stop at 15 ft. is mandatory. ....If a no decompression limit is exceeded by more than 5 minutes, a 15-foot decompression stop of no less than 15 minutes is urged....​

 

[tursiops]

I ahve never head the terminology eitehr of you used, and I have been a PADI professional for 17 years now. Here is what it says on the back of my RDP:

If a no decompression limit is exceeded by no more than 5 minutes, an 8-minute decompression stop at 15 ft. is mandatory. ....If a no decompression limit is exceeded by more than 5 minutes, a 15-foot decompression stop of no less than 15 minutes is urged....​

Yes, that is exactly what the RDP says.
But, in my (also!) 17 years of PADI professional experience, newish OW divers do not remember those rules and do not carry tables with them....less or more than 5 mins, 8 mins, 15 mins, 3 mins, 6h, 24h....so I've learned to try and provide some context and memory hooks. All they need to remember is 3 and 5. 3 min safety stop always. Less than 5 min over the NDL, add the 5 to your 3 and get 8. More than 5 min over the NDL, multiply your five by your 3 and get 15. Helps some folks, others glaze over. The 6h and the 24h are given the context of WHY.....most DCS presents itself in 6h, so stay out of the water and look for symptoms. The 24h clears your tissues, and also represents a bit of a penalty box you sit in for a day. Bad dog.

 

[boulderjohn]

The 6h and the 24h are given the context of WHY.....most DCS presents itself in 6h, so stay out of the water and look for symptoms. The 24h clears your tissues, and also represents a bit of a penalty box you sit in for a day. Bad dog.

It would be interesting to hear the official reason for the 6 hour rule, but I always assumed it was because the surface intervals on the table are governed by the 60 minute compartment, which is why the table clears out in exactly 6 hours; that is, a diver finishing a dive at the Z level will be totally off the table--done with the A group--in 6 hours.

But that is really off topic. This dive was governed by a computer, not the tables.