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Is this a Bad Dive Plan for Cozumel?

Discussion in 'Advanced Scuba Discussions' started by gasgirl, Aug 5, 2012.

  1. gasgirl

    gasgirl DIR Practitioner

    # of Dives: 200 - 499
    Location: Vancouver, BC
    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!
  2. Scott L

    Scott L Solo Diver

    # of Dives:
    Location: North Palm Beach, FL
    Ok, I will loan you my Oceanic Geo2 for the trip. :)
  3. RickyF

    RickyF Manta Ray

    # of Dives: 500 - 999
    Location: Oahu
    I dive a Sunto D6 and dove Coz this past May. I dove air on the first deep dive (100 ft) and 32% on second dive for 12 days with no issues. We always did at least 1 hr surface interval and my dives were all over 1 hour long. I did not incur any deco obligation. Set your computer for 1.6 PPO and 100% RGBM.
  4. gasgirl

    gasgirl DIR Practitioner

    # of Dives: 200 - 499
    Location: Vancouver, BC

    You can UPS it to me and let's hope that Canada Customs doesn't end up confiscating it!

    Many moons ago, we ordered a DVD of our dive trip from Anthony's Key resort - we never received it EVER!!!

    I suspect a Customs Officer is getting lots of enjoyment from the video of us frolicking with a pod of killer whales...

    ---------- Post Merged at 01:42 AM ---------- Previous Post was at 01:30 AM ----------

    Yeah, the problem with Suunto is that it really penalizes you for a surface interval less than 60 minutes. We already booked our 5 day 2 tank boat dives and the trip reports I have read stated they only did a 30 minute surface interval between dives.

    As I mentioned in the OP, I have been on 2 tank boat dives in Grand Cayman before and questioned the safety of the short surface interval. They were unwilling to extend the surface interval time and suggested diving with the Suunto going into deco as I described (but assuming the ASC time to clear by the time I reached the safety stop)..

    ... Can anyone reasonably confirm this is safe practice given the knowledge that all other computer brands are not going into deco with basically the same dive profile???
    sgariepy and Scott L like this.
  5. String

    String Master Instructor

    # of Dives: I just don't log dives
    Location: Grand Cayman
    The Suuntos are nowhere near as conservative as you make out for those profiles. They're within a few minutes of most other brands of computers.If you're not deco trained then don't dive them into deco. You aren't insured and are just guessing about safety. Id scrap the 30 minute surface intervals - i can't think of a single situation where a gap that short is going to be beneficial.
  6. racerx_

    racerx_ Barracuda

    # of Dives: 50 - 99
    Location: Singapore
    It's your life but I wouldnt do that on any computer.
  7. OzGriffo

    OzGriffo DIR Practitioner

    # of Dives: 100 - 199
    Location: Melbourne, Australia
    I wouldn't plan to bend your computer either. If you surface with a deco obligation, it's likely to go into lockout mode for the next 24 hours, and the op may not let you dive.
  8. RickyF

    RickyF Manta Ray

    # of Dives: 500 - 999
    Location: Oahu
    Suunto is known for it's very conservative profiles. I use another oceanic computer as a backup computer and the Suunto set at 1.6 PPO and 100% RGBM gives almost the same dive profile as the oceanic.
  9. Bigd2722

    Bigd2722 Solo Diver

    # of Dives: 500 - 999
    Location: Winter Park, fl
    I dove with a Suunto Vytec in Coz a few years ago, set for 1.4 ppo and on Nitrox (forget the %). We didn't do a really deep dive, but there were a couple in the 80' range. Only one time did I run into a 7 minute safety stop and it gave me no trouble (YMMV). There were a few 4 minute safety stops. Almost all of the dives were planned at 45-50 minutes and almost all of them stretched to at least 60 minutes.

    (One person on that trip did get bent and ended up in the chamber twice and was out of diving for 6 months. She was a very small person who had a few drinks the night before in the hot tub after 2-3 days of diving)

    YMMV but I don't hesitate to dive a Suunto to the edge of its limits. I do have two of them set to different ppo. Gives me something to compare and think about during my safety stops.
  10. bbarnett51

    bbarnett51 Solo Diver

    # of Dives: 500 - 999
    Location: Little Rock, Ar
    You aren't going to have a problem. I dive a Cobra and yes it's conservative but I'm ok with it.

    If you can get it then dive ean28 for your deeper stuff (assuming that mix fits your dive) that will give you a little more time.

    I don't recommend a 30 minute SI following a deep dive.

    Oh and to answer your question. Your computer might clear ours deco obligation as you ascend but not by 10min. An extended safety stop of a few minutes is not a big deal but don't get benched for getting locked out.

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