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Thread: First-hand account of down current, with video footage

 

  1. #121
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    NWGratefulDiver's Avatar
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    Quote Originally Posted by Splitlip View Post
    The way I see it, once the pair of divers broke away from the down current, they were in a run away accent. Dad even brings them both back down. I've nothing negative to say about that. When I did my open water, the rule was 60 ft per minute and there was no such thing as a safety stop.

    I'm quite certain I have exceeded 75 ft/min in my past and without a Safety stop. But then I was in my teens. In the vid, Dad did get them back down to be compliant with his computer.
    First off, based on the bubbles, I'd say the ascent was at a steadily accelerating rate, and as they approached the surface their ascent rate went well beyond 75 fpm.

    Secondly, I don't think taking a stressed out child back down would be a good idea. This was a short dive, and the risks of having something go wrong by re-descending far outweigh any potential benefit from doing an omitted stop ... particularly one which is more to satisfy the computer than out of any true need. A better idea would be to get him out of the water, put both divers on oxygen, and monitor for DCS symptoms.

    ... Bob (Grateful Diver)

    ---------- Post added April 24th, 2012 at 08:18 AM ----------

    Quote Originally Posted by Valwood1 View Post
    Well, dad-as-buddy may have made the mistakes that have been pointed out, and perhaps the problem would not have arisen if dad had been more attentive, but he at least was good enough in the pinch that this is only a near-miss thread.

    I've tried to stop a too-rapid ascent of another diver (not in a panic situation, but just due to too much inflation in the BCD, and only from 60'), and it's about impossible to do unless you have the person in a bear hug and can control the inflation of the person's BCD. Dealing with a panicked diver would be much more difficult, and the only real hope would be to get behind the person.

    Great point about nitrox. I'd never considered the potentially-lethal combination of nitrox and downcurrent on a wall dive, but I sure will now.
    One of the greatest difficulties of trying to arrest an uncontrolled ascent is that as you approach the surface, air expansion occurs at an increasingly greater rate the closer you get. Managing two BCDs makes the problem even more difficult. At a certain point it becomes impossible to let it out fast enough ... and you WILL go to the surface. Add inexperience and dealing with someone who is in or approaching a panicked state and you're in a very bad situation ... one that's easy to quarterback from the convenience of a keyboard, but almost impossible to manage in real life. These two did well to reach the surface unharmed.

    About the nitrox ... let's keep in mind this was a very short dive. Ox tox is a concern ... but it's also a cumulative effect. One certainly increases the risk with exposure to elevated PPO2 levels ... but the effects are rarely instantaneous. In other words, if you have to drop down beyond recommended PPO2 limits for a short while, it's not likely going to put you into a seizure. But you want to avoid it unless the emergency warrants such a decision, and you certainly don't want to make a habit of it.

    ... Bob (Grateful Diver)
    vladimir and InTheDrink like this.
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  2. #122
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    I would just like to join the others who thanked scurbyduck for posting the video. It's a good learning opportunity for all of us, and has elicited some good comments.
    InTheDrink likes this.
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    Adobo's Avatar
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    Quote Originally Posted by frontiernurse View Post
    I feel like an idiot. In the words of Denzel, "Explain it to me like I'm a six-year-old." I am not sure I understand what I'm seeing in this video so it is hard for me to learn from it. Someone mentioned "look at the bubbles at 4:35." OK. What do you see? What does it mean? What were the divers experiencing? I'm getting that they dropped down quickly, then the one with the camera was breathing fast and yelling. But why? What was he experiencing? How was that represented in the video? What was the father experiencing at that time? The video poster says, "spent the rest of the time trying to bleed both bcd's with one hand on the camera guy (my son) and one hand operating the bcds I couldn't keep up with bleeding the bcds down and was trying to flare but it seemed like all the bubbles were just pushing us up..." What does "bleed a BCD" mean? What does he mean by "trying to flare"? Was he trying to go up or down? If they were caught in a down current does that mean they inflated BCDs at some point then tried to empty them when they were in the video bubble storm? So at what point did they inflate to get out of the down current? Is that represented in the video? Or was it a horizontal current? I'm so confused! Was the video bubble storm created by the breathing of the 2 divers and the emptying of BCDs, or the currents? I'm a little frustrated because I want so badly to learn and understand and I think vagueness and lingo is getting in the way? No judgements on the actions of the divers... I just don't understand what happened. Sorry if I'm the only one with this issue. Feel free to ignore me.

    I'm with you. I don't understand what I am looking at in that video and certainly can't work out what, if any, lessons to walk away with.

    One observation though - the diver starts his descent at around 1:53 into the video. Maybe I missed it but I did not hear him adding any gas into his BCD until about 4:20 into the dive. That's a pretty long time to go on a descent without adding gas. By the time he gets to the top of the reef, he might be finning like mad to keep from descending further. And I did not hear him add more than 15 very short bumps worth of gas to his BC. Those short bumps is usually what I use to fine tune my buoyancy. You know, when I feel like I am having to use just a tad too much breathing to control buoyancy. And then panic sets in. At that point, he thinks enough to lay on the inflator. But still, probably never more than 3 seconds worth.

    General comment. May or may not be applicable in this situation - I cringe whenever I hear how much ballast divers use when they go diving. Every extra lbs of ballast that a diver brings that they don't need is an extra lbs of lift capacity that is no longer available for when it is truly needed.

    Everything from 5:30 to 7:30 on is just a sea of bubbles. If anyone here can extract anything meaningful from that segment, I'm interested to find out what.

    One question here - why was the buddy/dad wanting to go to 30ft? It was a 7 minute 30 second dive. How much inert gas loading is there on a dive that short? Wouldn't the greater risk have been AGE? If so, do you want to deal with that on the surface where you can get a victim on the boat or would you want to deal with that at 30ft?

    I am curious about this down current phenomenon. It seems like people are talking a lot about it recently. Maybe down currents can be downright scary. I don't know since I don't think I have ever experienced a down current. I am not sure I saw anything here that would indicate something like that. Again, maybe different in real life vs. what I am seeing in the video. To me, the more meaningful lesson here is that maybe that diver was put in a situation (boat dive) that he was not prepared to be in. If that were someone I cared about (spouse, child, friend, whatever), I would not put them in the water on a boat dive with so little experience. Shallow shore dive would be where I would start until they got more comfort being in the water.
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  4. #124
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    electrix's Avatar
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    My compliments to the dad, there was a lot going on and when your child is in the middle of it, it can be extremely stressful. I have a GoPro camera and distance is very distorted, things are much closer than they appear on the video.
    Last edited by electrix; April 24th, 2012 at 12:54 PM.
    I am their leader, which way did they go ?

  5. #125
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    Scurby or wife. Did the horizontal current Change directions at some point? If I am looking at the wall it would seem the current was moving to the right as that is the direction the camera was pointing
    Tim
    "They called themselves Guerrilla Divers.
    Composed of elite divers with Macho mentalities, back when men were men, and FEAR was a lispy companion of the common Man. It was a time before insurance liabilities, lawsuits or beauracratic regulation of the "sport". Guerrilla divers didn't need "Buoyancy Compensator Vests". In fact, "Anyone who needs a BC deserves to drown" was a popular adage. Exploration and the Hunt came first, excitement and fun followed. Safety was the stepchild of fitness, good reflexes and a cool head.
    This was a time of great Adventure."
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    I also want to thank scurbyduck for posting. I am sure that overall there is a geniune interest in analyzing this and helping everyone to learn from it and it is truly unfortunate that this process becomes insensitive and seems to evolve into personal attacks. I live in a glass house and it is not up to me to criticize you as a diver and much less to criticize you as a parent. I am very thankful to you for sharing this and I hope that this has not discouraged you from doing it again. I have watched this video over and over again in amazement. I have fortunately never been caught in such a situation and as I watch this I wonder what I would do. I have tried to read many of these posts to understand the learnings and I thought for those of us who are here to study and learn from this that I would start a succinct list of "lessons" that are particularly important when diving along a wall with essentially no bottom.

    1. Practice good buddy behavior. Descend together.
    2. Control your descent and descend slowly, watching your depth gauge. A downwelling is bad enough without the added momentum of a rapid descent. (I don't know what it was like in real life but from the video, the visual cues were not entirely obvious. I suspect by the time you see bubbles moving downward, its way too late!)
    3. If you get caught in a downwelling, swim away from the wall.
    4. If you are in a situation of bringing someone to the surface and need to increase buoyancy, add air to one, not both BCs, if you can. This will allow you to more easily regain control in the event of a runaway ascent.
    5. This one seems a bit more controversial, but, dive with air and not nitrox in situations where an uncontrolled descent well below your MOD is possible.
    6. Try to be nice to people who post their experiences on SB so that they will continue to do so and we can all learn from them.

    This is just what I have from the top of my head. I'm sure there are others.

  7. #127
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    Quote Originally Posted by Splitlip View Post
    Scurby or wife. Did the horizontal current Change directions at some point? If I am looking at the wall it would seem the current was moving to the right as that is the direction the camera was pointing
    At the start of the dive the current for me was out away from the wall. Others in our group said flowing north. But on the safety stop it brought us back in over the wall flowing to the south.

  8. #128
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    Quote Originally Posted by TSandM View Post
    You know, in reading more posts on this thread, one thing strikes me -- the instructor and student who got stuck at 165 were each rescued by the DM -- so the DM was able to go down to that depth, TWICE, and bring people up . . . that means that it was quite possible to get out of the situation, because the DM did it TWICE. We then have to ask: What did the DM know, or what could he do, that he could easily enough manage the problem, where four other divers were unable to do so?

    This is exactly my point earlier, however I used the father as the example. The father was able to negotiate the current without a problem to go to the son and help him. This is the reality that it's not about the conditions, it about the divers abilities and mistakes made that cause accidents. I suspect there is a corelation to training levels and how you view this video. The more training you have I suspect you look at the divers, the less you have you look at the conditions.


    Quote Originally Posted by NWGratefulDiver View Post
    One of the greatest difficulties of trying to arrest an uncontrolled ascent is that as you approach the surface, air expansion occurs at an increasingly greater rate the closer you get. Managing two BCDs makes the problem even more difficult. At a certain point it becomes impossible to let it out fast enough ... and you WILL go to the surface. Add inexperience and dealing with someone who is in or approaching a panicked state and you're in a very bad situation ... one that's easy to quarterback from the convenience of a keyboard, but almost impossible to manage in real life. These two did well to reach the surface unharmed.

    It's easy to quarterback from a keyboard, because the unmanageable run-away ascent wasn't an existing condition to overcome, it was caused by the rescuer, it was a created condition due to using both BCDs instead of one.


    Quote Originally Posted by Adobo View Post
    One observation though - the diver starts his descent at around 1:53 into the video. Maybe I missed it but I did not hear him adding any gas into his BCD until about 4:20 into the dive. That's a pretty long time to go on a descent without adding gas. By the time he gets to the top of the reef, he might be finning like mad to keep from descending further. And I did not hear him add more than 15 very short bumps worth of gas to his BC. Those short bumps is usually what I use to fine tune my buoyancy. You know, when I feel like I am having to use just a tad too much breathing to control buoyancy. And then panic sets in. At that point, he thinks enough to lay on the inflator. But still, probably never more than 3 seconds worth.
    This has been the point that the current while strong and angling slightly downward was not the mythical deadly down current that so many posters are now posting on scubaboard about, and asking if it's safe for them to dive in Cozumel because of these mystical downcurrents and incidents like this one recorded on video that appear to record how dangerous they are. The reality is this was self-induced, a too fast descent, bad habits such as the diver using only his legs and fins to stop his plumet, not adding air to his BC to get to neutral prior to feeling the pull of the current.

    This video to me is the opposite of what many see it as, it's a good example of how manageable a Cozumel down current really is. If you follow your training and dive conservatively there should be nothing to worry about. As TSandM stated, more than one diver on this same dive was able to easily descent and rise and move about in the current. The video shows the fine line in diving how you can be either in total control of yourself and out of control. It's a great video for study.
    Mike

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  9. #129
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    Wow! That's all I can say. Glad you guys got through it. I wonder if the hand holding buddy team clinging to the wall would have perished were it not for the DM coming to their aid. 77 cf of gas would not have served them very long at 165 while working and stressed.
    Tim
    "They called themselves Guerrilla Divers.
    Composed of elite divers with Macho mentalities, back when men were men, and FEAR was a lispy companion of the common Man. It was a time before insurance liabilities, lawsuits or beauracratic regulation of the "sport". Guerrilla divers didn't need "Buoyancy Compensator Vests". In fact, "Anyone who needs a BC deserves to drown" was a popular adage. Exploration and the Hunt came first, excitement and fun followed. Safety was the stepchild of fitness, good reflexes and a cool head.
    This was a time of great Adventure."
    www.sfdj.com

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    Quote Originally Posted by Splitlip View Post
    Wow! That's all I can say. Glad you guys got through it. I wonder if the hand holding buddy team clinging to the wall would have perished were it not for the DM coming to their aid. 77 cf of gas would not have served them very long at 165 while working and stressed.
    The instructor remembered nothing she didn't remember clinging onto the wall, and the student said he was a gonner had it not been for the DM.
    InTheDrink likes this.

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