how many dives is too much ?

[batman diver]

i recently went to a local quarry and did 4 dives , there are helicopters and planes etc to find and swim through and around , here is the thing i did four dives that day , on computer , tables made it a no no , i told a friend of mine at my dive school and he said it was stupid and dangerous , i thought he was being a tad too conservative and silly , i wanna dive , and dive a lot its fun, if a have the opportunity to do multiple dives y not

here are the dives
1.) 27m max for 27 min @ ave of 19 -1:40 surface time
2.)29.4m max for 37 min @ ave 14m -1:24 " "
3.)29.7 max 19 min ave of 18m -0:31 surface time
4.) 14m max 27 min ave of 6.6m

on the deeper dives did a ratio stop for one minute @ half the max depth and then did my 3 min @ 5

on tables i was bust on comp i never went into NDT closest i got was once and had 3 min , felt perfectly fine

what are your guys views ?
i was diving air ... did 2 refills using a 12l steel 200 bar ,

 

[bs63366]

So you are saying on your computer you did go into deco once? Or did you still have 3 minutes left before deco?

 

[DevonDiver]

What's a 'ration stop'? You taking Twinkies and beef jerky down with you?

You were within your NDL, but it could hardly be described as 'conservative' diving. I believe your training course may have mentioned something about the need for "diving conservatively". Did you mention to your instructor, at that time, that you felt conservative diving was silly?

The NDL on your computer is not a magical boundary that provides safety...and there are a lot of other factors that the computer algorythm cannot account for. As a novice diver, buoyancy issues, runaway ascents and incorrect ascent speeds are a potential risk that demands great 'safety margins' with your diving. Other factors such as water temperature, air (post-dive) temperature, body composition (fat %), post-dive exertion and incidence of PFO (are you checked for this?) can lead to DCI hits, when otherwise within NDL and with proper dive/ascent profiles.

Was it dangerous? No.

Is it 'ideal'? No.

Are there risks? Yes.

Is it a personal choice? Yes.


Obviously your friend has a different level of 'acceptable risk' than you. It doesn't make him right or wrong.

Just be sure that you fully understand the risks...and how they can apply to you... then you can make an informed personal choice.

I recommend reading the DAN Annual Reports and BSAC Annual Incident Reports, to get a feel for the risks and consequences that accompany your personal diving decisions. Be aware that both reports attribute the majority of incidents to a "failure to adhere to the basic principles of safe diving practice" (of which conservatism is a major one).

If you need further information about safe diving, I strongly suggest that you investigate the following agencies' publications...

PADI Safe Diving Practices.

BSAC Publication on Safe Diving

 

[Quero]

We do four dives a day routinely on our liveaboards here in Thailand. The dives tend to be longer, but we don't go to nearly 30 meters for three consecutive dives. Given that three of your dives were quite deep, and if the water was cold, you'd have to take that into account and add 4 meters as a precaution when calculating your risk, your dive profile was rather aggressive. But I wouldn't necessarily call it dangerous or stupid. Nor would I call your friend silly or too conservative. He is simply less willing to take the level of risk that you have chosen to accept, that's all.

Did you and your dive buddy discuss your dive plans with depths, times, contingencies before doing these four dives?

 

[batman diver]

yes i got hungry so had to eat some rations ha ha , excuse the spelling.
water temp was around 22 degrees , it was a fairly hot day , we had a snack after every dive and lots of fluids , we did discuss the plan before each dive , the rule was call it b4 10 min to deco , or 70 bar , except for the 1st dive when we said dont go into deco, as this dive was the more important one , find the chopper and send up SMB , that one we were 3 min from deco , with regards to accent rate i'm very pedantic about a slow asscent , some times battle with ears so go up super slow to avoid reverse squeeze ,
so would i be correct in assuming the dives weren't dangerous , but not exactly conservative ... ie i want lucky to not get bent , but should maybe have skipped the last dive ? also i thought and am up for correction that perhaps the last dive was a good idea as it would have involved a lot of off gassing ?

how does one then find their limits and adjust them to be more safe ? is there a way ? to find a balance maybe ?

p.s i am going to doc to check for a PFO the amount of ppl with one is surprisingly high

 

[Quero]

In my opinion, your dive planning could have been a good bit more thorough than just "don't go into deco" or "stay more than 10 minutes from deco."

You were wearing a dive computer, and at the very least, you could have used it for your dive planning before each dive. It will take into account your theoretical N2 load based on your previous dives and your surface interval up to the time you enter the planning mode, and it will tell you what your NDLs are for the depth you plan to dive to. If you think your bottom times are too short for what you want/need to accomplish, the solution is to extend your surface interval. Since you were diving in a quarry with stuff sunk down on the bottom, your dives were probably mostly spent at depth, so it's pretty straightforward to look at your computer 15 minutes or so before your dive to see what it gives you for an NDL.

You should also do some basic gas planning, particularly when diving at those depths. You should have an idea of your typical air consumption and be able to plan how long you can stay down within the NDL. Just because an NDL says you can stay for X minutes doesn't mean you will have enough air to actually do so--it depends on your consumption. So, while you should be sure to know your turn pressure (you said 70 bar) and watch your NDL data on the computer, neither of these should be a surprise to you as you dive if you do some basic dive planning before you splash in.

That is how you find your limits and adjust them in order to be reasonably safe. If you don't know how to do this, go to your (NAUI?) instructor and get some additional theory time in so that this stuff is clear to you.

 

[ajduplessis]

Batman. The dives you described doing at Miracle Waters in general looks fine. I would however consider extending your SI time to around 2 hours on the deep (puma) dives. I also assume you corrected your DC to the appropriate altitude?

I will be doing some dives the Sunday there, not sure if you would like to meet up, always nice to meet new guys. PM me if you would like to join.

 

[DevonDiver]

how does one then find their limits and adjust them to be more safe ? is there a way ? to find a balance maybe?

If I was doing diving like that (mutliple deep dives), then I'd definitely be cranking down the conservatism settings on the dive computer.

If you're using a Suunto - get the dive log software and download the dives. This provides graphs of your nitrogen tissue loading over multiple dives. You might find those graphs shocking!

What you need to remember is that your body tissues absorb and release nitrogen at different rates. Here is a 'layman's' description:

The 'fast tissues' absorb nitrogen quickly and then release it equally as quickly on ascent. The slower tissues absorb it slowly... so that amount of nitrogen contained in those tissues shouldn't become a big issue for recreational dives (when you load the 'slow tissues' they are slower to off-gas... hence the need for deco - a very 'slow' ascent).

Over multiple deep dives, you are repeatedly 'topping up' those medium-slowest tissues, as they do not fully off-gas during the surface interval (takes around 48 hours). So you are effectively getting back into the water on each subsequent dive with higher and higher amounts of nitrogen stored in slow release tissues.

As these 'slow release' tissues become the driving force behind your deco obligation - you also need to be aware that the amount of deco needed can increase very, very rapidly (think 'exponentially') and can still accumulate even after you have started your ascent. Some recreational divers get into some minor deco.. and notice that it 'clears' on ascent... or is very minimal. They then assume that this will be the case in every instance. It isn't. When you're dealing with slow tissues... it can really catch you out.

On a single recreational dive, the 'fast' tissues control your dive. On multiple deep dives, slower 'tissues' start to control the dive. This is why NDLs get shorter on each subsequent dive. It is also why your ascent rate becomes increasingly more critical as your nitrogen loading grows. There is an increasingly lower tolerance for error.

If bubbles do occur... their location will determine the type and severity of your DCS hit. Bubbles forming in slower tissues. (like the spinal cord) are much more serious than quicker tissues (like the muscles or subcutaneous fat).

Being "3 mins from deco" is physiologically very different on your first dive, than it is on your 4th deep dive. The nitrogen is in different places, with different off-gassing rates... and with different consequences if you got a DCS hit.

 

[Quero]

One more thing...

also i thought and am up for correction that perhaps the last dive was a good idea as it would have involved a lot of off gassing ?

Any time you are at increased pressure underwater breathing air you are loading more N2 than you would be if you were on land breathing the same air. So no, you would actually not be accelerating your offgassing by doing the fourth dive unless you were doing it on a decompression gas mix instead of air. You would, in fact, be delaying your eventual completion of offgassing, which ultimately happens by being out of the water on land until the N2 in your body equalizes with the N2 in the air around you, or by breathing nitrogen-poor gas such as oxygen.

 

[CamG]

Greetings Batman as Devon has suggested on deeper dives I try to give myself a little longer SI's just to be conservative.
When we are not diving beyond 60 ft I will do as many dives as I have gas and my computer will allow.
Now bear in mind that each one progressively gets easier, shallow or drift little effort.
What I focus on is dive planning and being smart out of the water.

When diving deep I do things very slow and methodical.
In and out of the water, not because I am narced but to watch my level of exertion.
I have heard some totally preventable DCS hits from carrying tanks to far to fast.
So I just chill and cart or carry slow and easy. This is diving not a job!

Have fun and dive safe. Be conservative in your dive plans and relax on your SI's.
It is about enjoyment and fun savor the moments!

CamG Keep diving....Keep training....Keep learning!