Can I dive to 40m (130ft)?

[billt4sf]

Short answer: You probably could pull that off, but it's not a good idea. Wait until you have more experience.

- Bill

 

[charlier]

Excellent thread, with many good comments and ideas. From limited personal experience, taking diving ~40 m in remote Indonesia, I will only take experienced divers that have the skills set, mental and physical fitness, and experience to such depths.

 

[Peter69_56]

I really have no words to express how many things are wrong with this... You most likely went into mandatory deco, hence the 2 stops. Did you have any sort of gas plan? Obviously not, if one of the other divers had to share. Did you discuss your "safety stops" on the surface. Did anyone look at tables or planning mode on a dive computer to see how long you could stay at depth without going into deco as from the sounds of it you are not decompression trained. Or did you just take what the guide said as gospel?

NDL at 40m is 5 minutes. How long were you at 40m. And then if you stayed at say 30m for any length of time say 2-3 minutes you were probably in deco.

I virtually never dive with a single air source now. On virtually every dive I either have twins, single and sling, rebreather and bail out. This is regardless of the depth. To dive to 40m with a single air source is increasing risk. In our area, vis can be bad so why increase the risk on a single air source and to boot go into deco on same air source. If you have the personality to push boundaries, then at least minimise the risks as much as you can. Dive like as though you are a solo diver, in that way if you have your buddy there too its a bonus, but should you lose them and then have an issue hopefully your redundency covers it and you are safe. I always have 2 masks, redundant air, 2-3 knives or cutters, 3 torches, 2 DSMB's and 2 finger spools. Non of it takes up much room if stored correctly, and I am then fully redundent for me (and also my dive buddy should I have one).

 

[boulderjohn]

NDL at 40m is 5 minutes.

Under what algorithm?

For both the PADI RDP and the US Navy tables, it is 10 minutes.

 

[Peter69_56]

Under what algorithm?

For both the PADI RDP and the US Navy tables, it is 10 minutes.

ZHL16-C +GF, 40/75 on Multi Deco

If I use ZHL16-C +GF, 100/100 its 11 minutes on Multideco

Also SSI tables quote 5 min at 39m

Depends on the tables and the risk you chose to take

 

[markmud]

I'm going on a dive trip in a couple of days and one of the dives I want to do will be at 40m.

I've done 32 dives, 7 of which have been at 30m (100ft), with one at 35m. I have a PADI AOW certificate where the recommended depth is 30m. The dive will be on air.

Do you think I have enough experience to try doing dives of up to 40m? Do you think the PADI Deep specialty is worth it (I personally don't but if someone can convince me to do it...)?

Thanks!

Hello Youseef,

I apologize in advance for parsing your words.

You can dive to whatever depth you want; the Scuba Police won't be there to cite you. Is it smart? Probably not.

If you wrote that you had 50 logged dives with a steady depth progression to 120 fsw (37 meters) I would say go for it--with a good buddy and a dive plan.

A dive plan that includes air consumption at depth. You would need to know your SAC/RMV. V-Planner is software that can help you create the dive plan quite easily.

Is the PADI Deep specialty worth the money and time? I don't think so. I went for Tech 40 instead. It is the first truly comprehensive dive training for the recreational diver that PADI offers. What I mean is this: the preceding certs except for OW, and Rescue, are more like participation certs. Learn a few new skills, dive a couple times, and then get your new cert card in the mail. Their value is that the instructor is supposed to review basic skills with you. You know, repetition!

Here is the progression I recommend for the recreational diver (not a tech diver):

1. OW
2. AOW
3. Nitrox
4. Rescue
5. Solo/Self Reliant/Independent Diver
6. Tech 40.

At 3.16 ATA of nitrogen, narcosis starts to creep into your dive planning. As you know, the deeper you go, the harder you work, and the less you breath (to conserve your single aluminum 80 breathing gas supply (77 cubic feet), the more susceptible to narcosis you are.

I would not want to attempt a CESA from 130 fsw (40 meters). What is your buddy's RMV/SAC? He/she is carrying your bailout supply of gas. I feel that a CESA from 50 fsw is doable for me. From 30 fsw, a CESA should be no problem for me. A CESA from 40 meters is a scary proposition for me--I am not ready to die or totally get effed up.

No, since you asked the question on Scubaboard, you are probably not ready.

markm
Read Caveat Emptor below:

 

[boulderjohn]

ZHL16-C +GF, 40/75 on Multi Deco

I have my computers set to ZHL 16-C with GF 50/80, and I will confirm that on an NDL dive, you will go into deco long, long before anyone using recreational dive computers. However, their idea of deco at that point means you have to do a 1 minute stop while everyone else is doing their 3 minute safety stops. It takes a while before you accumulate the deco needed for a 3 minute stop.

 

[Blasto]

Do you think I have enough experience to try doing dives of up to 40m? Do you think the PADI Deep specialty is worth it ?

There's no cut and dry point where you're ready or not. Every dive is a risk - the deeper, the more risk. Experience improves your ability to manage an emergency, but depth is just one of the factors that affect it.

PADI Deep is a very thin course. It's certainly better than nothing, it will help you gauge your narcosis susceptibility, and actually place you at that depth, under supervision, adding a bit to your confidence. OTOH, with a good instructor, almost every course is worth it, simply for more instruction time, plus diving in a much smaller group.

ZHL16-C +GF, 40/75 on Multi Deco

IDT picking a bottom time at which a deco algorithm gives zero stops is a good way to estimate recreational NDL. Gradient factors are a safety margin - for, among other things, deco complications. Separate hi/lo GF particularly outright account for deep stops.

 

[wedivebc]

People who are planning NDL dives using multi deco with GF or VPM really don't understand what those things do.
For NDL dives stick to a rec computer using some type of modified Buhlmann or RDP.

 

[J322Y]

Warning--video has adult content!

I would think someone should have called the dive when it became obvious that the effected diver was very uncomfortable. I don't just mean that he was cold, but at one point he asked if they should surface, and he kept making references to how there was nothing to see, it was boring, etc.