First dive at 40 meters - Newbies recreational

[johndiver999]

OP claims his computer setting is such that if he exceeds 30m the computer will plan a 2 minute stop at half the max depth dived and another 2 minute stop at 12m.

Yes I missed that comment, so I subsequently deleted my comment. 2 minutes at 20 meters seems a little wacko to me for a bounce to 40 meters, but whatever.

 

[Blackcrusader]

Instructor Vs DM. Long debate, I guess.

No debate at all for me.

A dive master is not qualified to certify a student on a training dive as far as I know. a DM can assist an instructor on the dive but your instructor was not on the dive. I am not an instructor so lets wait for an instructor to reply incase I am in error.

In any case he exceeded the max depth of 40m allowed for his course as well.

 

[Storker]

After the fact, I thought that I had pretty much well managed the dive. Now, not so much. If I was in deco, I clearly messed up. I was neither trained nor prepared for that and I hate not being in control :-( . I won't tell my wife until I get the whole thing sorted. Thanks.

This is what I like about SB. People getting qualified feedback and learning from their errors.

No harm done, but that was because this time you were lucky. We're usually lucky, but it's bad practice to factor in luck in your dive planning. Normalization of deviance (look it up on google, there's a pretty damned good presentation about that) and all that.

 

[Blackcrusader]

Actually he just mentioned that his computer setting will plan a stop at half the max depth, not the second stop.

I believe both you and I accept that he did indeed go into deco and his computer gave him a deco obligation at 12m for 2 mins. I've never heard of a computer deciding you need a "safety stop" at 12m only a deco stop.

 

[Storker]

you say we were in deco?

This is one of the things about riding the NDL. If I'm in deco, or just close to my NDL, going straight for the surface may very well not be a good thing. However, if I do a triangular profile dive I will probably be quite fine, since my slow ascent basically offgasses me on my way up.

But if SHTF and I have to get up NOW, I might need a chamber ride.

 

[Storker]

I've never heard of a computer deciding you need a "safety stop" at 12m only a deco stop.

Some Suuntos may impose a "deep" safety stop at half of max depth. Or somewhere around there. And if you truly violated your NDL, the mandatory stop would be at 3m or 6m.

Unless your 'puter runs a really weird algorithm.

 

[Blackcrusader]

Some Suuntos may impose a "deep" safety stop at half of max depth. Or somewhere around there. And if you truly violated your NDL, the mandatory stop would be at 3m or 6m.

Unless your 'puter runs a really weird algorithm.

Well he wrote he had one mandatory at 20m so how do you explain another at 12m for 2 mins and the final safety stop at 5m?

Students riding NDL on a first dive to 40m on training dive? Say it aint so

Thanks for clarification about the Suunto.

 

[Storker]

how do you explain another at 12m for 2 mins and the final safety stop at 5m?

I can't. Just contributing a data point, that's all.

 

[Edward3c]

Part 1 of 2:

We were three: the DM, me and my wife and partner in dive.

Red flag: I will only do a depth progression past 30m on a one-2-one basis.
Red flag: who was the dive leader for the dive? You, your wife or the DM?

Everyone with a 12 liters steel tank pressurized at 210 bars. No pony. Just a cylinder with reg and octopus at safety stop (5m) on the anchor line.

Red flag: Had you done the gas management calculations to confirm there was enough gas to get you back to 5m whilst sharing one cylinder.

Sunny weather air 27 degrees C. Water temperature 26 degrees C.
Calm water at the surface.
(Small fishing) Boat dive.
This was the last SSI deep dive training session.

Back roll entry then regroup at the surface and descend to a 12 meters underwater sand platform. I am glad that I finally managed to continuously equalize my ears as the first 6 meters have been awful in a handful previous dives. No problem this time. Kneeling at the bottom: Buoyancy control: ok, mask integrity: ok, breathing rhythm: ok. SPG: ok. Computer: ok. Viz: 20 m. The dive starts at a slow pace. It is actually a slope dive where you gradually descend. So gradually that my eyes fail to inform me ( I need to work on that). If my ears did not let me know every 0,3 or 0,5 bar pressure increase, I would dive oblivious of the descent (without the gauge and computer). The dive plan is clear, we start shallow (less than 20 meters) for a very limited time so that we are comfortable with our sensations then if everyone is ok, we go deep. 10 minutes after water entry, the DM gives the descend sign.

Red flag: If you diving deep you should go straight there not mess round in the shallows.

SPG at 180/ 190 bars for everyone ( strangely, in our last dives, the three of us seem to have almost the very same gas consumption). It is still a slope. The scenery and aqualife are mesmerizing at such a point that I am surprised when my computer alerts me that I am approaching 40 meters. I must have equalized mechanically. We still have light from the surface. I was expecting dark, cold temperature, a new world but nothing really. No Nitrogen narcosis ( I was disappointed as I said that I wanted to face it and beat it. Don't call me fool please. I like making jokes).

Red flag: NN starts its narcotic effects from 15m onward. I get students to complete a prepared ‘noughts & crosses’; they can’t believe what they wrote when on the surface,

My previous max depth was 33.4 and as we stop at 40.5, there is no new feeling. However, for a recreational diver, 40 is the saint barrier. The ultimate psychological goal. And we are happy ( Even if it is not the first time for the DM, he played along). As we are congratulating each other (40,5 m might not be much for some but it was an achievement for my wife and I), computers start beeping: 1 minutes to NDL. WTF! We must have descended too slow and spend too much time between 30 and 40.

Red flag: What decent rate did you plan. Tables can use anything from 10m/s to 30m/s (BSAC 88), if you don’t stick to them you’re diving outside the plan.

Damned! We can’t stay any longer. And we forgot the camera ( no picture to immortalize the moment). SPG at 150/ 160 and going down fast. We started to ascend parallel to the wall reef that was the end of the dive and guess what? Impossible to reach the reef. An adverse strong horizontal current has decided otherwise. I knew it was too easy before. You need to deserve it. No panic ( Good Lord, bless the dive briefing), my wife and I decide not to fight the current and slowly ascend while being dragged ( we have a boat at the surface and the "skipper" is very good).

Red flag: Someone on the surface is of no use to your during the dive. All they can do is report you are missing and your entry point.

At some point my wife joins hands and then the macho surfaces . You wife count on you, man. Don't f... up! Show confidence and control. As we ascend, I monitor my depth and realize that we are not progressing. It must have been 30 seconds that we are flipping upwards and we only moved from 40 to 37. What's wrong? Usually, it is the other way around. We must slow down not to ascend too fast. Is there a physical bareer that no one on SB told me about? Is the situation serious? Then my brain takes over. What if? What if we can't ascend as planned? What should I do? Is there a down current (not uncommon)? Think, think, think fast? Your wife's life depends on you. Don't panic, don't get exhausted, think then act accordingly.

This is one of the signs of NN.

I decided to increase the amplitude of my flips but not the frequency so that I could keep my breathing steady. I fought the urge to inflate our BCDs

Red flag: You were likely overweighted for the depth, insufficient gas in your BCD, or you had dumped too much.

(we are still breathing and we have air so there is no immediate emergency) and I made a very quick calculation (worst case scenario, we consume 5 times our SAC. 5x11 l/min round to 12, it is 60 l/min. with 150 bar that is 1800 liters, we have 30 min so no need to panic). So we continued to fin. Then, the computer again. Stop at 20 meters: 2 minutes. At this point, I would have been happy to be at 20 meters but I realized that I was at 28. Relief. We continued finning calmly and at about 25 meters, we saw the most magnificent reef we had ever seen. Wonderful colors but mainly yellow. Never seen such a beautiful scenery even at the Louvres. My wife released my hand grip and we swam towards the reef as there was no current there. I decided that we would do the stop there and inform the DM.

Red flag: At 20m your slow tissues are still on-loading which will increase the decompression requirements at shallower depths.

The DM was slightly above us, still in control.

Red flag: What did they do to made you think they were managing the dive?

I don't know how long we stayed there but probably more than 2 minutes. Then the computer said: 12 meters - 2 minutes stop. So we ascended, complied with the stop and went to 5 meters for the 5 minutes stop (computer said 2 minutes).

Red flag: You were diving a ‘hope it works’ dive, no gas planning.

We surfaced with 40 bars without using the safety cylinder.

Red flag: I’ve had depth gauges out by 40bar, you could have been on a near empty cylinder.

Summary:
Total dive time: 40 minutes.
Max depth: 40,5 meters

When we surfaced, I was the proudest man underseas. My wife said: this is the most enjoyable dive we've had (so far, all my dives have been with her). It was WONDERFUL!!! And then I said: it was hot at some point when you took my hand and she replied: I was enjoying it so much, our first real challenging dive, a real wonderful dive, that I wanted to physically share it with you. I loved it. Let's come back tomorrow. So much for the guy who thought he was the hero of the day .

We do not intend to go deeper than 40 meters anytime soon unless we decide to go for tech diving one day ( not before 2021 H2). We do not even intend to go back to 40 meters just for the sake of it but only if there is something to see but this dive has been an achievement, a consecration and a confirmation that diving will now be a big part of our life.

Red flag: You got away with it, but you’re in line for a Darwin Award if you don’t develop the skills to plan and execute dives. See what @Storker said about “Normalization of deviance”.

 

[Edward3c]

Post 2 of 2:

It’s been a wonderful 50 days journey from the day we visited a dive shop for the first time to now AOW with 37 dives. And that's only the beginning. Even if we are both 51 years old.

But how much diving have you done without a DM or an instructor, that’s when you start to learn.

Hello, I will try to respond point by point.
Before the dive, I had ran a complete simulation on my PC. My main concern was not exceeding the NDL but being short on gas as there was recently a thread on SB about whether it was safe to dive at 30 meters with a single cylinder.

Red flag: If you don’t decend as predicted in the simulation you’re not following the plan.

- NDL at 40 meters is 5 minutes. The simulation had given me 3 minutes max at 40 meters. That's why I was surprised when my computer indicated 1 minute after maybe 30 seconds. As the plan was to ascend straight to 25 m, deco was out of the equation so there was no deco emergency procedure. The decision to start at 20 meters was only to make sure that we were comfortable before going deeper and all the parameters were green.

Red flag: If you’re diving deep you should go straight there not mess round in the shallows.

One thing that we should have had maybe was a pony, but when I raised it to the instructor, he said that the emergency cylinder at 5 meters was enough.

Red flag: What do you think the coroner would make of that if you or your wife ran out of gas and drowned? Your responsible to ensure you have enough gas to complete a dive, not some random DM.

- I mentioned that the descent was too slow because for me, it is the only explanation for 1min NDL warning so soon. In the simulation, we were at between 20 and 40 for 10 minutes and the descent to 20 meters should take 2 minutes.
However, the ascent was not too slow. It was just a matter of perspective and perception on my part. From the computer, we ascended from 40 to 25 at 7 meters/ min.

As an ascent rate that could be considered fast; I’m often below 5m/min.

- The DM was above us and he was alert. When I said afterwards that I was pleased that neither my wife nor I did panic, he said that he did not see any sign of panic and that we had acted both as we were trained and briefed. I think that we need to factor in the stress that I was probably feeling for my first dive at 40 m. Even though, I always say that I am immune to stress, well, sometimes, I overthink too much and make calculations and assumptions in the heat of the moment that might complicate things.

Red flag: What did they do to made you think they were managing the dive? Panic isn’t always visible.

- I agree on a safety margin at 40 m. I am a big advocate of safety margins. And we had none in terms of NDL and a too small one on air if something really bad had happened. Buddy breathing would have been ok but a down current to say 50 meters would have left us in a bad predicament with only the computer to tell us what to do to deco. I am confident that we could have managed getting out of it ( I have never experienced a down current but this is one of my fears so I fully programmed my mind to react to that. Hence, the 45 degrees as we could not use the reef as a shelter).
So, there are goods and bads in this experience as in any dive especially when you do something new but more goods than bads.
Bads are: not enough safety margins in NDL and air. I should have ran more simulation scenarios.
Goods are: all the rest. We followed the dive plan and all went well.

Red flag: No you didn’t follow the plan. If you did you wouldn’t have exited with 40bar.

I might have been affected by narcosis after all but I was still able to rapidly calculate how much breathing time we still had.

You were Narked, or your lying. Everyone will be narked at 40m, its how you manage it that matters.