Is this a Bad Dive Plan for Cozumel?

[gasgirl]

:laughing: Certainly nothing personal there, just your hardware. I'm such an air hog that I am often one of the first to ascend, but I do other things to compensate - like lining up larger tanks to dive, and I hate to come up early because of a bud's overly cautious computer - which has happened to me a few times. Many divers start out with overly cautious computers that penalize divers unreasonably, as compared to the "more liberal" units that are as safe as Padi tables - no guarantees but a good record. So, when you decide to upgrade is up to you, but I just don't like diving with my bud's silly computer in control.

On the other hand, it wouldn't be hard to find info on this board that would suggest avoiding diving with me. :shocked2: You have quoted some old comments of mine that were interesting in review of old ideas, but then I am mostly a fumbling tourist diver.

I do hope your chosen Op doesn't rush you on your SIs. Being first in the water for the first dive, then last for the second dive would add some time to yours, and of course diving Nitrox on the second is a nice idea.

When are you going to be in Coz? I know of an Oceanic I might borrow.

Hee Hee! We are there August 19-25th. We are planning on attending your Birthday Extravaganza on Aug 21st!!!

Do you have TWO Oceanics you can borrow?? My DH has a Suunto Vyper and he has to buddy with me!

BTW, DH and I met in Canyon, Texas in 1986 . He was already a certified diver when we met. He did his OW check-out dives in Blue Hole, New Mexico. Is that near your neck of the woods?

 

[Mr Carcharodon]

Gasgirl,

You need some sort of plan. Since no one really can predict the various penelties you computer spits out following it may not be much of a plan, but unfortunately a couple extra minutes at 50, 40, 30 feet is just the start of a plan. Of course there are tables that you probably already know, ratio deco, and decompression procedure classes. For what its worth my Sunto is in gauge mode and I use RD. If your going to ignore what your computer tells you you need to be able to come up with your own plan. I'd be circumspect about doing so.

 

[fdog]

Hmmm. Gasgirl, I admire the way you've kept your composure. I'll pass on some observations:

As far as I can tell, there's over a half dozen different "models" that can be used for calculating obligation (and thus, NDL).

Every one of these models have cases where they are conservative. And, they all have places they are aggressive. This even applies to the much-abused Suuntos.


I believe the biggest mistake is "model hopping". Usually I use a Suunto, but here in Coz, it's really cutting into my times...! I'll switch to an Aeris (DSAT model) while I'm here. This leads to inconsistency in the big picture.

Pick a model, stick with it over a large variety of dives, and learn how it treats your body. If you always feel great, then stick with it - it's doing something right, eh? If you notice when it makes you feel tired, then identify a model (and thus, a computer) that's better for the way you dive. In the meantime, do what it says to learn it...and keep yourself safe.


Everyone's physiology is not the same.


All the best, James

 

[farsidefan1]

Bad habit to start breaking the rules. Easy to push it too far.

If you're going to use a dive computer, adhere to it. If it accumulates deco time, be prepared to work it off.
Sure, Suuntos are pretty conservative, but needlessly so? I think not. It simply allows for more safety margin.
Deco calculations are not exact science, but rather based on theoretical models that seem to yield pretty safe results.
You might say it comes down to "what odds are you willing to consider for your safety?"

Now, very few divers get bent, despite a multitude of errors committed by some of them. Yet, I have been in Cozumel and seen a very healthy, young, experienced diver get bent on a routine, uneventful dive, despite his dive computer's "guarantee" of safety.

As an aside, have you been screened for PFO, which increases your risk?

Your worst case is you could get bent or die, but happily someone else has a chance to claim a relatively new conservative dive computer.

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You have far more control over your surface intervals that you realise. Before you commit with a dive operation, you explain to them your requirements. If they cannot be respected, you're with the wrong outfit. No one forces you to jump into the water. Remember, it's your safety that's at stake. This overrides whether they'd like to go home a little earlier.

There are a TON of truly excellent dive ops in Coz. If the one you have picked is talking about 30 minute surface intervals I would suggest you switch immediately. The decompression chamber in Coz is pretty convenient but I liked outside a whole lot better. They locked the damn door! I like how Kilili put it (hence quoting him above). Oh, and yes I had an ASD (virtually same as a pfo), since then, repaired. With a one hour + surface interval your computer should be fine. There are not many dives in Coz where you are going to exceed 100 feet. I understand the concerns with down wellings but 2 facts. Significant ones are not common unless you go to some of the more advanced dive locations, and my understanding from what I have read in other threads (so check with Dr. Deco or one of the other med types) if you did accidently wander below your 32 or 36% momentarily it is not like your gas instantly becomes toxic. But get yourself up above those levels immediately. Most first dives in Coz seem to be between 80-90 feet. And guess what? The dive op will know you are less experienced (be sure to let them know in case the DM is blind) and they will pair you up with other newer divers so your profile will be more conservative anyway,

 

[fdog]

<snip>

My questions for Nitrox divers in Cozumel are:
1. Do people commonly dive air on the first tank and then EAN on the second tank in Cozumel? ie. Will using EAN give us a more reasonable NDL on this second dive?
2. Is yes, would you recommend diving EAN 32% or 36% giving the typical second dive profiles in Cozumel?
3. Is anyone aware of oxygen toxicity problems diving with Nitrox on the first deep dive?

My questions for those familiar with Suunto computers are :
1. Would you allow the Suunto computer to go into deco and assume it will clear as you slowly ascend (10 ft/min) with mulitlevel stops for several minutes at 50 and 40 and 30 feet?
2. If yes, what is the maximum deco obligation that you would incur (assuming, of course, that this still falls within the gas plan)?

<snip>

I guess I should have answered your questions from the OP:

1. Do people commonly dive air on the first tank and then EAN on the second tank in Cozumel? Not me, I'm the straight-Nitrox-throughout kinda guy. If I'm going to get benefit from something I don't want it frittered away. ie. Will using EAN give us a more reasonable NDL on this second dive? Of course. Whether it's more benefit (second dive only) for the week of diving overall...depends.

2. Is yes, would you recommend diving EAN 32% or 36% giving the typical second dive profiles in Cozumel? Recreational, I always take it as rich as I can get it.

3. Is anyone aware of oxygen toxicity problems diving with Nitrox on the first deep dive? Recreational, I've never seen this, been on a trip where it's happened, or know anyone that's seen it.


My questions for those familiar with Suunto computers are :
1. Would you allow the Suunto computer to go into deco and assume it will clear as you slowly ascend (10 ft/min) with mulitlevel stops for several minutes at 50 and 40 and 30 feet? No. I will not go into deco intentionally without redundancy. Assuming you'll clear on ascent is predicated on nothing going wrong. ....And what if you don't clear?

2. If yes, what is the maximum deco obligation that you would incur (assuming, of course, that this still falls within the gas plan)? Again, my mind hears this as "How bent would you like to be?" I'll take none, thank you.


All the best, James

 

[gasgirl]

There are a TON of truly excellent dive ops in Coz. If the one you have picked is talking about 30 minute surface intervals I would suggest you switch immediately. The decompression chamber in Coz is pretty convenient but I liked outside a whole lot better. They locked the damn door! I like how Kilili put it (hence quoting him above). Oh, and yes I had an ASD (virtually same as a pfo), since then, repaired. With a one hour + surface interval your computer should be fine. There are not many dives in Coz where you are going to exceed 100 feet. I understand the concerns with down wellings but 2 facts. Significant ones are not common unless you go to some of the more advanced dive locations, and my understanding from what I have read in other threads (so check with Dr. Deco or one of the other med types) if you did accidently wander below your 32 or 36% momentarily it is not like your gas instantly becomes toxic. But get yourself up above those levels immediately. Most first dives in Coz seem to be between 80-90 feet. And guess what? The dive op will know you are less experienced (be sure to let them know in case the DM is blind) and they will pair you up with other newer divers so your profile will be more conservative anyway,

So I finally got this email back from the dive op we are currently booked with:

'Regarding the diving situations, for us to make the trip to Maracaibo and the devil&#8217;s throat, you will have to check with the dive shop, so they can make possible the trip, but we can arrange it if the conditions are favorable. For the surface interval, we will have to check in the dives that you make, as we are managing a group, not all of them would like to wait that long, but we can make that notification to the dive shop and they can work something out, but I don&#8217;t to guarantee the 60 minutes each time.'

Although it does not sound like they have a standard policy for a 60 minute SI that some other dive ops may have, it certainly sounds to me like they will try to accomodate us if they can. We have already booked the dive package for this trip so I think we will just go with it.

FWIW, I do know how to use the Dive Plan mode on my Suunto. I have done what Mike suggested on a boat dive in Grand Cayman when I was diving air and I politely objected and showed the DM that I had a very limited bottom time for my second dive after the 30 min SI. He said it didn't matter as it would be a multi-level profile dive.

Also, my last dive trip was a liveaboard in Palau - so I know how to drift dive in strong currents, do live drops, make blue water ascents, and deploy SMB's at depth. During that trip, we dove EAN 32% on every dive, and we had at least 90 min SI between dives, so we had no issues whatsoever with any of the NDL times for 25 amazing dives over 7 fabulous days. My max depth was 106 ft. My average bottom time was between 60-65 minutes. I never actually encountered one but I did read up on what to do in a downcurrent.

I used the Scubaboard forum to familiarize myself for the dive conditions and dive sites in Palau before I went. There was lots of good information about what to expect and I felt well prepared when I jumped in the water.

So to summarize MY dive plan for using our Suuntos while diving in Cozumel:

Dive air for the first dive (likely to exceed MOD on EAN32% if the right conditions are right and we go to the sites we want)
Dive EAN36% for the second dive (with a MOD of 95 ft)
Do a 1 minute stop every 10 fton the multilevel dive
(as slow ascents minimizes the 'penalty' imposed on repetitive NDL's by Suunto)
Do a 3 minute deep safety stop at 1/2 MOD
Do the recommended 3 minute 15 ft safety stop
Do our best to entertain our fellow divers in our group during the SI
(to extend it as close to 60 minutes as possible)
Take our time to do an extra long buddy check for our second dive
(to be the last ones in to get wet... unless there are other Suunto divers in our group)

I think if we stick to these strategies, it will be all good, and I will not have to be exiled from Cozumel.

 

[DandyDon]

Hee Hee! We are there August 19-25th. We are planning on attending your Birthday Extravaganza on Aug 21st!!!

Do you have TWO Oceanics you can borrow?? My DH has a Suunto Vyper and he has to buddy with me!

BTW, DH and I met in Canyon, Texas in 1986 . He was already a certified diver when we met. He did his OW check-out dives in Blue Hole, New Mexico. Is that near your neck of the woods?

Oh, cool. I'll look forward to meeting y'all. He's been diving since then and he went with a Suunto? Well, some folks seem to like them.

Your just posted dive plan seems good, altho I think you could plan on 32% for most first dives if you wanted to - depending, a 3 minute deep stop seems a bit much to me - but with the multilevel aspect of most dives I think you can work something similar in ok. I guess your computers have Nitrogen loading bars so you can see it as it loads and off-gasses.

How did you two end up in Canyon? I suppose you know where Plainview is. The Blue Hole, made famous on Rt.66 for the Dust Bowl immigrants fleeing and in the "Grapes of Wrath" is in Santa Rosa, NM...

 

[shoredivr]

'For the surface interval, we will have to check in the dives that you make, as we are managing a group, not all of them would like to wait that long, but we can make that notification to the dive shop and they can work something out, but I don&#8217;t to guarantee the 60 minutes each time.'

I don't read at all that they are willing to extend the surface interval to normal and safe 60 min. The dive company is indicating that not all of "a group" of divers would like to wait that long. If this is really true, that the dive op is willing to make shorter than 60 min surface intervals because a few members of the group want to do this risky dive plan, can you please tell me what the name of this op is, so I can avoid using them.
Thank you for bringing this thread up. Perhaps i have been lucky, but in 14 years of diving in many locations around the world, I have not run into an op that would agree to short SIs. If this is all true it does not reflect well on this op.

 

[TSandM]

I may be reading your planned ascent strategy wrong, but I would recommend against doing ten foot stops all the way up. The Marroni studies that are quoted on the DAN website showed that this was actually the worst profile for bubbling, of all the ones they used. Most of us do 10 foot stops starting from half our maximal (or average) depth, and use a 30 fpm ascent rate for the deeper portion of the dive.

 

[tracydr]

I may be reading your planned ascent strategy wrong, but I would recommend against doing ten foot stops all the way up. The Marroni studies that are quoted on the DAN website showed that this was actually the worst profile for bubbling, of all the ones they used. Most of us do 10 foot stops starting from half our maximal (or average) depth, and use a 30 fpm ascent rate for the deeper portion of the dive.

I was just going to mention the same thing. With 10 foot stops, you keep on adding nitrogen and will actually cause worse bubbling with increased nitrogen load, because of the added time at depth. Go to 1/2 MOD, then start the stops, just as TSandM recommends.

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I don't read at all that they are willing to extend the surface interval to normal and safe 60 min. The dive company is indicating that not all of "a group" of divers would like to wait that long. If this is really true, that the dive op is willing to make shorter than 60 min surface intervals because a few members of the group want to do this risky dive plan, can you please tell me what the name of this op is, so I can avoid using them.
Thank you for bringing this thread up. Perhaps i have been lucky, but in 14 years of diving in many locations around the world, I have not run into an op that would agree to short SIs. If this is all true it does not reflect well on this op.

I read this as they will only do a one hour safety stop if everybody insists. If anybody wants a shorter stop, they're going with the shorter stop. Doesn't sound like a reputable dive op or safe plan to me. Two deep dives with a short safety interval? I'd do the nitrox on both dives and keep myself above 100 feet.

BTW, I dive a TUSA Imprex and a Suunto. My husband dives Suunto. I don't notice any difference to speak of between the Suuntos and the TUSA. They both will both show minutes to deco at almost exactly the same time. Just bought an AERIS, so I'll see how that compares. (I needed a nitrox computer, + my TUSA was dying).