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What I learned today...

Discussion in 'General Scuba Diving' started by Wibble, Apr 15, 2019.

  1. Wibble

    Wibble Fish don't talk
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    Thread to talk about things we learned about diving related matters, possibly whilst diving, possibly as a result of something not going right...

    i.e. something we could all benefit from knowing about.
     
  2. Graysyid

    Graysyid Active Member

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    Just ordered the book Under Pressure, not sure if anyone else has read it. Its meant to be a must read for all divers and is about reducing human error factors when diving
     
  3. Wibble

    Wibble Fish don't talk
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    I was diving with a buddy this weekend. (This is rather uncommon for me as I tend to dive with "independent" divers, sometimes together, sometimes alone)

    The dive went really well. It's early in the season and I was helping my mate with a new kit configuration. Was lovely to see him comfy and stable in the water.

    It was the ascent that caused problems. We'd done about 45 mins at 25 metres, 27 max, both on nitrox him on 36%, me on 32%. We ascended with him driving the ascent whilst winding a small reel on the SMB. My Shearwater computer showed I'd got a couple of minutes stop at 6m to clear the deco, and from knowledge & experience, I knew this was around what I'd expect.

    He was very slow in the ascent, starting it at 18m. We'd discussed on the boat that he would like to do a slow ascent to 'mock' a greater deco loading, so this wasn't unexpected. My deco had cleared during the 9m stop and with him on more O2, his would be definitely clear. We finally arrived at 6m and I was expecting him to clear and ascend. Being a bit rough, the reel was bouncing, so pulling him around a bit, the wind drifting the SMB as well. When he went up a bit, I assumed that he was going up, so I went into "going to the surface mode" and started my final ascent. My mistake [1].

    I was on the surface next to the SMB, boat 50m away, expecting him to surface. I waited and he's still down and dropped even further. WTF I thought; why's he not coming up [2]. Waited another minute then descended to see what's happening [3]. My ear blocked (happens quite often on a descent after diving), so had to surface to clear it. Waited another minute (about 4 mins now), and descended. He was at 6 metres with a very perplexed, confused even, look on his face [4].

    I signalled about the deco to which he replied 26 minutes left! I knew from experience and from "ratio deco" approximations that this was clearly complete nonsense [5]. Even if diving on air, this was miles out (would expect no more than 15 mins of air deco given that profile, and that it would be clear by now).

    So my quandry. Buddy was obviously transfixed with his (only) computer (a Suunto Helio [6]), My ready reckoner estimate said we were clear. My experience said we were clear. Both my computers said we were clear.

    I signalled "thumbs up" to him and he was adamant that his computer was telling him he would be bent. Again I questioned his deco. Again it was 26 mins.

    Now getting concerned. Being object fixated isn't good. Checked his gauges (wasn't overly subtle about this either). Plenty of gas but a very upset diver who's really confused. Backed off a bit to get out of his face and have a ponder. Went back in to try to get him to ignore the computer and just ascend. Which, thankfully, he did after a minute or so.

    All OK. Back on boat. All lived. Total dive time was 70 mins. Minor joshing about being "Suuntoed".


    Later, I whacked in 21/36 at 25m for 45mins into Multideco: shows 42 mins of deco! Don't know if this is the case, but could explain it [7].


    Lots of learning points! But was a nice dive.


    [1] - What a crap buddy I am. Too much diving on my own. Need to spend more time team diving to reset this skill
    [2] - Obviously something wrong with the buddy, get yer arse back down to sort it out
    [3] - Could have been time critical?
    [4] - Confused and transfixed diver: the stuff of rescue scenarios (narked, etc.)
    [5] - I approximate with simple rules of thumb, for shallow dives I use 30 mins at 30m on 32% with 10 mins per 3m shallower/deeper (e.g. 24m = 30+10+10 = 50 mins), so my 2 mins of deco was just a 'safety stop'. If diving on air I'd approximate it to 20 mins at 30m on air with 5 mins per 3m shallower/deeper (e.g. 24m = 20+5+5 = 30 mins. 45 - 30 = 15, so about 15 mins of deco), again this would be clear given the amount of stop time we'd done
    [6] - I just don't trust Suuntos; another regular buddy used to have one and it always kept us down much longer.
    [7] - Computers could be fallible, especially if misconfigured
     
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  4. Graysyid

    Graysyid Active Member

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    On a shallow dive at Farnes last year with two other divers we was told by the skipper to stay within a certain area of land due to the current. It was my first saltwater dive and I wasn't comfortable, sure with the direction one of the other divers was taking us during the dive (into the current) . He was finning in front and didn't turn around so had no way of signalling him with my concerns. unsure whether to go with my gut instinct that he was leading us into minor trouble or just follow, I decided to surface. Once on the surface the skipper told me not to descend again as the current was pulling us out. Eventually the other two ascended and were picked up.

    At what point do you go with your own instinct and abandon your buddy (buddies in this case)?

    TBH the dive was that shallow the risks were minimal, but on deeper dives it may not have been the case
     
  5. Wibble

    Wibble Fish don't talk
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    Personally I've always seen UK diving as needing an independent mindset as it's so easy to loose your buddies or for conditions to rapidly deteriorate. You should have the skills and planning to be self-reliant, even when diving with others. Binning the dive because you feel uncomfortable is the right choice in most conditions. Standard recreational diving practice is the "if lost, look around for a minute then surface".


    My question/issue is when should one become more "assertive" with your buddy when it's obvious that they're confused or fixated. The clear case is imminent danger. But at the other end of the spectrum it could be 'me' who's wrong (as I often am) or misinterpreting what's going on.
     
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  6. Dave Whitlow

    Dave Whitlow Super Moderator
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    A correctly configure Suuntos is quite predictable and the planner is quite useful.

    Looking at Sunnto dive planner (with P0 setting) and (last stop 6m) you can see what happened.

    A dive to 27m leaving the bottom at 45 minutes using 36% provides a deep stop at 13m and a safety stop at 6m but ...
    A dive to 27m leaving the bottom at 45 minutes using air will give a deep stop at 14m and have him arriving at 6m with 32 minutes to surface.

    He clearly hadn't configured his computer correctly and wasn't monitoring TTS during the dive. Was there any discussion about the amount of deco being done? Was there any communication during the dive about TTS?

    So long as he had gas to breathe then I support his decision to stay in the water until his computer told him it was safe to surface.

    He needs to re-read his computer manual and check personal setting and last stop depth.
    He should analyse his gas and set his computer correctly before each dive.
     
  7. snowman

    snowman Active Member

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    I think a lot of it comes down to 'know your buddy' (not always possible on a dive boat) and be trusting enough to accept that if they're saying there's an issue, that there is.

    Of course, anyone can get confused and/or narked, so you (or they) may not be right, but unless they're clearly wrong (Up is down, etc - which might indicate a serious problem with them!), you have to accept the dive is canned if they say so.

    If you think someone is swimming the wrong way, let them know. More often than not, the act of questioning them, will make them admit they haven't got a clue or reassess and confirm they're right or put it right.

    Sometimes they're thinking "It must be this way because no-one's saying it isn't...."

    My sense of direction under water is legendarily poor, but even I will question my buddy if I think they're wrong. If I'm wrong, we've just checked, no harm done. If they are, we sort it out.

    M
     
  8. Dave Whitlow

    Dave Whitlow Super Moderator
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    He was floating at 6m with plenty of gas so there was no reason to be 'more assertive'. There are plenty of reason to leave him alone and merely support him. This is what a good buddy would do.

    Being more assertive would increase his stress level and this could result in buoyancy issues (down or up) and increased gas consumption. Just chill and watch the plankton!
     
  9. Wibble

    Wibble Fish don't talk
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    So it looks like the computer was configured for air, not Nitrox 36.

    Running the numbers through MultiDeco it seems my ready-reckoning needs tweaking a bit for when no accelerated deco gases are available -- another learning point.

    And it really stresses my tardy 'buddy check'.

    Seems this was quite an educational dive!
     
  10. Vanny

    Vanny Active Member

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    I have always stressed to divers they must fully understand their PDC , the pertinent word there is Personal , dive computer. You can’t expect a buddy , however good, to interpret a PDC their not familiar with.

    To your buddy he needs to fully understand the comp , run practice dives etc. Clearly he didn’t actually read the comp , probably looked at but didn’t actually read it.

    Good buddy skills are as important to develop as much as solo/self reliant skills. This is something the BSAC system does hands down better than any other organisation I’ve yet to come across.

    From other threads I believe your buddy was on a new kit configuration. I would hazard a guess he was a little task loaded.

    Glad it all turned out ok and plenty of learning points.
     
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  11. JohnL

    JohnL Well-Known Member

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    Perhaps on a similar note, the case of the disappearing wreck. We dropped down an anchor rope near a wreck site in Gran Canaria and the instructor headed for it but it was not there. I could see him hesitating until a large school of fish parted to reveal the wreck only 10 or 15m distant. He was beginning to doubt the coordinates of the marine gps. Or I was told when I was learning, the compass is right, never trust your gut.
     
  12. Wibble

    Wibble Fish don't talk
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    Definitely task loaded. New kit config for buddy. New boat for me; small boat, rough sea, bouncing around, issues with one diver missing the shot needing a pickup... stressy!

    Big learning point was about how stress affects one's thought processes, especially mine. Nobody ever gets more clever when jumping in.

    Maybe the real lesson here is to have a break from focussing on technical skills development and re-aquatint myself with some team skills, maybe even "dive leader" skills.

    Question: where can one get "dive leader" skills or workshops? It's not something that TDI do. I'm not a member of BSAC and am rather sceptical of the 'big' agency's pyramid scheme.
     
  13. gg

    gg Administrator
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    Moved to other thread
     
  14. jps

    jps Active Member
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    There's a place for a suunto..... and it's not on me.
     
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  15. Tribal Chestnut

    Tribal Chestnut Well-Known Member
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    Edited for accuracy:

     
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  16. Dave Whitlow

    Dave Whitlow Super Moderator
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    I disagree. A Suunto is perfectly adequate for no-stop diving, as done my the majority of the diving world, and for diving with limited decompression. Until someone buys it from me (£100), I still use a Suunto Vyper for dives in Chesil Cove.

    For diving involving significant decompression there are more suitable tools available although.
    In gauge mode a Suunto, and runtime slates, remains a potential backup option.
     
  17. Wibble

    Wibble Fish don't talk
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    I'm like Dave on this. My Suunto d9tx is fine for non-deco dives, or those with a couple of mins of deco. It's of no use for a deeper long deco dive which needs the ascent profile maintained. Not least because the display's too small, the controls fiddly, and the algorithm is just wrong for these dives (compared with Buhlmann 50:80).

    So fine for recreational diving, useless for technical diving.

    It's on my wrist as a last resort backup and a dive log.
     
  18. John F

    John F Active Member

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    I did a 50M dive the other weekend with my usual buddy. We were at 50 for 4 minutes then up to the 23 m shelf. Before I got to 50 I had 4 minutes of deco showing on my Eon steel and by the time we got to 23M I was showing 14 minutes of deco, my buddy had a Shearwater and that never went into deco.
    So I think my next purchase will be a Shearwater.
     
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  19. JohnL

    JohnL Well-Known Member

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    As I am a non-deco diver and intend to stay that way, unqualified to comment (but when has that stopped anyone!). It just doesn't seem right to choose your dive computer on the basis that it gives the least deco time. I understand the earlier comments about Suunto - my Zoop is perfect for my diving but no way is it designed for technical divers.
     
  20. Dave Whitlow

    Dave Whitlow Super Moderator
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    I presume the Suunto still offers the options to change conservatism ('personal settings')? Back in the days when I owned a VR3 I used the Suunto dive planner set to P-2, the least conservative, and the dive profile was quite sensible.

    If you are in the market for a new computer then OSTC computers are also worth looking.
     

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