What is the "typical" surface interval for two tank boat dives in Cozumel?

[Christi]

Oh yeh - I can't believe I didn't make the nitrox suggestion - DUH - haha!

 

[vlkr]

re geezer gas (aka nitrox) i am a big fan because.. well because i am an ol geezer.
re suunto problems - if you are 100% confident in your ability to do so, you can remove the battery and then put it back in. that will erase the lock out problem. warning do not do this if you really have a debt. better to de-gas and miss a dive. also, do not do it if you are not sure how to remove battery. one more caveat. i would not open up a computer while there is salt water around (as in on a bouncing boat).

 

[1erCRU]

Gasgirl,

Just a thought: why not borrow an Oceanic (or other) computer from your dive op and run it side by side with your Suunto for a few days for comparison and give us a report (in the computer forum please!). I'm not suggesting you switch between them, stick with your Suunto as primary, just observe and record the differences, if you are that motivated (and you might be!). I think you may find the exercise a somewhat interesting non-event, however you might find something to share.

I envy you on your first trip to Cozumel, I made mine nearly 3 decades ago and still remember those dives.

 

[jbjclj]

Hey remember (most of you won't) when your SI was calculated off a table and a wrist watch? With the ensuing argument about the differences between NAUI and PADI tables! The SI calcu was made only after you had changed your own tanks, eaten a torta or couple of tacos and washed it down with a beer or two, all the while drifting in the sun on a panga smelling of fish and gasoline and the captain fishing non-stop?

Troublesome image? Yes, we did have concerns about exceeding the lifetime of the ice for the ride back to town!

This I can relate to!

 

[gasgirl]

Lorenzoid,

This is my original post on the other thread in it's entirety:

Is this a Bad Dive Plan for Cozumel?

Attention: I am seeking opinions from divers who have first hand experience with Suunto computers only please! (For those who do not dive with Suuntos and do not know about the problems with the over-conservative algorithms that penalize repetitive dives with short surface intervals, please refrain from responding with non-productive critical comments!)

Brief background:
Shortly after purchasing my Suunto Cobra, I recall being advised by an instructor in Grand Cayman that it would be fine to incur a deco obligation at depth up to 10 minutes as it would clear during my multi-level profile as I ascended and did my safety stop. I opted not to voluntarily put my new computer into deco on that trip but I was diving in conditions and sites that easily allowed me to modify my depth to be shallower that the rest of the group.

Shortly after that, I switched to diving Nitrox, and I no longer came even close to my NDL times on my repetiitve dives, and so I never had issues with Suunto being too conservative even when we were doing five dives a day (albeit with longer surface intervals than 60 minutes) on any of our subsequent dive trips.

Fast forward to the present:
We will be heading to Cozumel in a couple of weeks and based on what I reviewed from other trip reports, I am concerned that the dive profiles for our two tank boat dives we wil be doing may be problematic for us as we are diving with Suunto computers.

Because of conditions specific to Cozumel (ie. swim throughs at depth and possible strong currents), I am anticipating that the first dive of the day in Cozumel may be at a depth greater than the MOD for EAN 32% so we were planning on diving air. Then we are assuming that there will be a very short 30 minute surface interval before the second dive, so we are planning to dive wither EAN 32% or EAN 36% to help extend our NDL time for this second dive. However, my understanding is that Suuntos really impose serious penalties on the NDL's for surface intervals shorter than 60 minutes.

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)?

FWIW, I did do a search on SB forum and found numerous comments condoning this type of practice to counter the overly conservative limits of the algorithm. For example, here is a quote from lamont in another thread:

"Realistically on a Suunto with 5 minutes showing (2 mins mandatory + 3 mins safety stop) you're not in much danger at all. You can probably even go across that by another 5 mins at depth and while the Suunto will probably be telling you 10+ mins of deco to do, you'd be fine blowing it off if the absolute worst case happened to you.

So yes, I realize that I have no technical training, and that I am diving a single AL80 tank, but I am also getting the impression that in the worst case scenario, it is the computer that will get bent, and the dive plan is still within safe recreational limits on pretty much any other computer.

I am hoping to get responses that will help me figure out how to best dive safely in Cozumel with our Suunto computers - and please do not suggest buying new computers is the answer!




With the helpful feedback I got, the "strategy" I decided to use was: air for the 1st dive, enjoy a nice SI appropriate for the 1st and 2nd dives planned, and EAN36% for the 2nd dive. This was clearly posted as the happy conclusion to my other thread.

It is not some elaborate workaround as you have implied, but it is different than what I have had to do on my previous trips where I just used EAN32% for all my dives.

The specifics for me that were unique to Cozumel was having to think about which gases I could use which would help extend NDL without exceeeding MOD.

What was also interesting to learn, is that the the average surface interval in Cozumel tends to be longer than the average surface interval in Grand Cayman - definitely (good) news to me!

There are many discussions on the SB forum that have debated the experience level required to do drift wall diving in Cozumel and that is a whole other topic - many feel it is not "easy".

Unfortunately, there is a report on this forum of a recent accident earlier this year in Cozumel where a diver was uncomfortable with the conditions, ascended early, and she was never found.

I personally like to be confident that before I jump in the water, I am capable of achieving my objectives for my dive - that is how I am trained and how I dive.

I am OK with the fact that we obviously have different philosphies and we choose to dive differently.

I am not OK with the negative vibe that has been created by your posts and having to respond to your criticisms.

I again respectfully request that, going forward, you refrain from further unproductive comments about me and how I choose to dive.

FWIW, there have been other people who have posted that they have appreciated reading and learning from these threads.

Isn't that the whole point of this forum?
​

 

[diverrex]

It can be interesting, and sometimes frustrating, to see how these threads evolve. Someone asks some very specific questions to try to increase their knowledge and incorporate that new knowledge into their diving and they end up getting 1,001 replies of all different kinds including buy new gear (computer) and almost always lots of criticism of what they are doing or thinking. Luckily enough of the responses are actually to the point and useful to make the whole exercise worthwhile if not frustrating that you have to do so much sorting through the wheat from the chaff (sp?).

 

[cvchief]

It can be interesting, and sometimes frustrating, to see how these threads evolve. .

How bad can a thread be with one of the Dutch just BEGGING for an Austin Powers reference?

 

[gasgirl]

Gasgirl,

I am impressed with your concern for safety and wanting to understand what you are getting into, I wish MORE divers were like this. You would probably be mortified to know how many "experienced" divers we see that don't even know how to set their computers, let alone use them properly. With that said, and I don't mean this with any disrespect - I do think you are over analyzing this just a bit.

Of course the surface interval is important and plays a factor, but it's not going to make much of a difference on the first dive of the day, which is the dive that has the most potential to put you in unplanned deco. It is the deepest dive and the way the SUNNTO algorithms work is that they load you up at depth. Where some computers start giving you credit back as soon as you start ascending, the SUUNTO basically requires you to get to the 30 to 40 ft mark before it will start giving you credit back - so many SUUNTO users end up with a few minutes of "unplanned deco" pretty frequently.

I am not ENCOURAGING you to go into "unplanned deco" but I'm just trying to put it in perspective for you. This is not TRULY deco, and not a reason to be concerned - conscious and alert of it, yes, but you are not going to get bent because you were a couple of minutes into "SUUNTO deco". If you get bent, I assure you there are other factors playing into it (that's another totally different topic). The explanation is far too in depth to go into here, but maybe one of the real techies will have the time and energy for it.

The bottom line is as you said, be responsible for your OWN safety and dive plan and WATCH your computer.If you hit that "unplanned deco" point, signal the DM that you need to ascend. Ascend to the point you need to and you will see your computer clear within a few minutes...and another VERY SIMPLE (I KNOW there is more to it, especially for true deco dives) rule is if you have a deco obligation, CLEAR it! As log as you clear it in an instance like this and then follow with a proper safety stop (I never do less than 5 minutes), you haven't "put yourself in danger."

If you watch your computer throughout the dive, and do a true multi-level dive not spending too much time at the max depth, you will be ok. But if you do need to ascend shallower than the rest of the group, signal the DM and stay above them if you can until you have completed your stop(s). There is not a DM worth his/her salt that wold force you to stay down if your computer is putting you in violation mode. The really good ones will also deploy a signal marker/sausage for you so that you are not surfacing in the "dark" - and so that the boat captain knows he has a diver surfacing. Discuss this with your DM on the boat as part of the dive plan to make sure you are on the same page - you'll probably find that you are.

I think you will be pleasantly surprised at how professional and qualified the DM's here are if you are with a quality operation, and you ARE booked with one. Unlike the weekend warrior DM's and Instructors (some of who claim to have more dives than DM's that have been diving 15 years 5-6 days a week - cracks me up because in most cases it would be impossible - it's a chest thumping thing) , these guys are diving every single day in the open water and manage divers of every level, every personality, have seen every computer, and know every dive in their sleep. They've handled more real life situations than you can imagine.

I'm not saying to go on a "trust me dive" - but I am saying that you are in good hands and you are not going to be given an unsafe dive plan. I said it before, but the guides are also planning the profiles for themselves, they dive virtually every day, week after week - they need to keep themselves safe as well. If THEIR computers are not going into unplanned deco, then yours shouldn't be either if you are following the dive plan!

I hope that was all as clear as mud - haha!

Moral of the story, hydrate, relax, hydrate, have fun, hydrate and WATCH YOUR COMPUTER - oh and HYDRATE!

Thanks, Christi. I appreciate you taking time out of your busy schedule to point out some good tips of safe diving. Personally, I routinely do all of these things when I dive, and I totally agree these are good habits that go a long way in mitigating the chances of a "hit".

You don't have time to read all the threads, but in the Advanced forum, I did mention that my last trip was a liveaboard on Palau and I was totally comfortable diving in those conditions. What was different from the Palau trip was that my max depth for all 25 dives there was 106 ft and so I was able to use EAN32% on the entire trip; because we plan to do some of the more advanced sites like Maracaibo Wall and Devil's Throat, we will have to use air on those first dives.

It is unfortunate that there has been some negative chatter that may have come across in this thread as concerns of unsafe dive ops when there was none. Let me assure you that I am totally confident we will have a fabulous time diving with Blue Angel.

 

[Zman96]

Gasgirl,

Just a thought: why not borrow an Oceanic (or other) computer from your dive op and run it side by side with your Suunto for a few days for comparison and give us a report (in the computer forum please!). I'm not suggesting you switch between them, stick with your Suunto as primary, just observe and record the differences, if you are that motivated (and you might be!). I think you may find the exercise a somewhat interesting non-event, however you might find something to share.

I envy you on your first trip to Cozumel, I made mine nearly 3 decades ago and still remember those dives.

I did this with Christi's DM Pedro. I use a sunuto gekko and I borrowed one of his back ups for a couple of days to use along with mine (think his was a Mares not sure though). I found on most every dive I was running into deco on the gekko and on Pedro's I would have 8-15 minutes of time left.

 

[gasgirl]

...Moral of the story, hydrate, relax, hydrate, have fun, hydrate and WATCH YOUR COMPUTER - oh and HYDRATE!

Just thought I would share a link to this urine colour chart I found online earlier this year: http://www.urinecolors.com/dehydration chart.pdf

And no, this is not a passive aggressive way of telling anyone to piss off!