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    Down Currents

    Regarding the ADV, I thought it was only Meg divers that are trained to shut off the ADV for ascent. A well designed and properly functioning ADV should not matter on ascent whether it is on or off. The concern with leaving it on is accidental injection of hypoxic mix while shallow. Since you didn't specify that this was a deep dive, I would guess that you wouldn't have had a hypoxic diluent if you were on CCR and therefore shouldn't be concerned about shutting off the ADV. Your situation is a good justification for keeping the ADV active for the entire dive.


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    Re: Down Currents

    Quote Originally Posted by Larry0428  View Original Post
    Not sure if I am posting in the correct area. I recently experienced a severe down current while diving Open Circuit and taking photos with a large DSLR camera set up. It was at the end of an interesting drift dive basically along a wall quite close to shore at a Komodo dive site. I had completed my safety stop and was about to ascend when I was caught in a down current which within what seemed a few seconds had taken me from 5 to 25 meters. I still kept going down to 35m despite fully inflating my wing. If wasn't so scary watching your exhaled bubbles descend faster than yourself is quite an unreal experience. Anyway I tried to swim out away from the island and eventually got out of the extreme down current. I still had to fin pretty hard to get back to the surface. When I did eventually surface I was more than 400m out from shore, so it was quite a wild ride!

    Now my question is, has anyone experienced anything similar on a CCR and what did you do? I'm imagining if I was on the breather (Inspo Vision) the rapid descent would have have spiked my PO2 quite considerably as I usually only switch to low set point at about 4m. Then I'm wondering I usually turn my ADV off on ascent, but with such a rapid unplanned descent and my hands full with a camera would I have had sufficient presence of mind to either turn the ADV back on or manually add via the MAV? Finally, while I don't think I panicked and my thought process seemed quite clear, I was pretty keen to get out of the down current and back to the surface, so if my ascent was too rapid on the Breather I'd risk going hypoxic on the way back up if I wasn't thinking clearly. Just interested in opinions and experiences so I can formulate a bit of a plan in my mind or practice some skills to prepare for such an eventuality on the breather (hopefully a very remote possibility as it's the first time anything like this has happened to me).

    BTW I usually dive quite conservatively so had plenty of air left at the end of this dive but I blew threw pretty much all of it by the time I was back on the surface, so that conservatism certainly saved my butt.

    Cheers
    Larry


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    Hi Larry, very scary story, glad you lived to tell the tale.

    I have been in several serious down current situations on CCR, the worst were on the north coast of Papua New Guinea and in Alor, Indonesia. The fact that you managed to survive this on OC is frankly amazing, you must be one cool customer.

    The key points, IMHO, are first to not panic, which is made easier because on CCR you almost certainly have enough gas to stay under as long and go as deep as necessary to get out of the situation. The next thing is however much gas you have, you must still be careful with your gas management. In Alor, we were trapped in a very bad up/down current, which took my dive buddy down to 60M and up to the surface multiple times. She almost ran out of gas because she was trying to use her wing to stabilize the situation, constantly filling and venting it, in addition to all the gas she had to fill and vent through the counter lungs. For this reason, and a few others, I do not believe that 2 ltr onboard cylinders are sufficient for any open ocean CCR diving. It doesn't matter whether you have BO or not, you will not have time to do anything, much less fumble with gas blocks, shutoffs or an OC BO regulator in a situation like this. And yes, she was carrying a BO cylinder, but had no chance to use it until she reached calm water 15 minutes later.

    Luckily, as planned, I deployed my SMB as soon as we hit the water, so the boat could keep track of us while we swam in a shallow channel looking for a pod of dolphins. But the Capt. did not look at the chart and was unaware there was a 60+m drop off at the end of the channel and we got caught in what was effectively an underwater waterfall.

    I experienced the same up/down as my buddy, but on a much smaller scale, because I was able to hold on to the SMB reel and only went up and down over 0-15m. With my spare hand, I was able to depress my OPV and manually to vent gas from the CLs and my nose, and depress the ADV to add fresh gas as depth increased. It is for this reason that I wouldn't ever worry about an O2 spike, because if you are being forced down, you will necessarily need to add dil to fill the CLs to get a breath, probably manually, as most ADVs are not responsive enough in a seriously fast down current. I didn't even think about my wing as I knew it wouldn't help in such a current. Your CL volume is what you should be focused on because you must breathe first and foremost, see previous comments about not panicking just because you are being pushed down, or worrying about the depth, because you have a CCR.

    Also, given this very real possibility of unforeseen strong currents when diving in places like PNG or Indonesia, and because of basic simplicity concerns, I am not in favor of inline ADV shutoffs, and part of the reason I don't like the BOVs I've tried, because they all leaked and required an inline shutoff. Maybe there are newer ones that are better and don't need shutoffs. And when diving with BO that is the same as my onboard, I have my BO gas supply plumbed into the dil reg and leave the valve open, just in case, so all my gas is available to the loop at all times without any fiddling.

    The other salient point about a situation like this is how crucial it is to have physical access to your CLs for the purposes of being able to vent and add gas manually in such a fast moving situation. Things for me would have been way worse if I had back mounted CLs and an OPV I couldn't easily reach. But with my thoughtfully designed Prism OTS CLs, I had only to move my hand a few inches around my chest to dump or add large volumes of gas from the CLs in seconds. That, plus nose venting, gave me more control over my depth changes and lessened my vulnerability to an over pressure lung injury, than if I had BM CLs, no easy access to the OPV and could only vent through my nose.

    The incident in PNG was just a straight down current and took myself and my CCR diving Capt. down to 60+m in a bad tidal down current. There was no sign of the current on the surface, before we jumped, either. It took us 30+ minutes, all our strength climbing up hand over hand and multiple rests to get out of it. We were 2 healthy men, totally spent, sitting on the deck after, thankful we weren't diving OC. Otherwise we would've gone through an AL80 in a few minutes and both been dead.

    IMHO, my CCR kept me calm and ultimately alive in those situations because of the amount of gas available and the time and ability to think things through... -Andy
    Last edited by silent running; 14th September 2014 at 20:48.

  3. #13
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    Down Currents

    Quote Originally Posted by silent running  View Original Post
    Hi Larry, very scary story, glad you lived to tell the tale.

    I have been in several serious down current situations on CCR, the worst were on the north coast of Papua New Guinea and in Alor, Indonesia. The fact that you managed to survive this on OC is frankly amazing, you must be one cool customer.

    The key points, IMHO, are first to not panic, which is made easier because on CCR you almost certainly have enough gas to stay under as long and go as deep as necessary to get out of the situation. The next thing is however much gas you have, you must still be careful with your gas management. In Alor, we were trapped in a very bad up/down current, which took my dive buddy down to 60M and up to the surface multiple times. She almost ran out of gas because she was trying to use her wing to stabilize the situation, constantly filling and venting it, in addition to all the gas she had to fill and vent through the counter lungs. For this reason, and a few others, I do not believe that 2 ltr onboard cylinders are sufficient for any open ocean CCR diving. It doesn't matter whether you have BO or not, you will not have time to do anything, much less fumble with gas blocks, shutoffs or an OC BO regulator in a situation like this. And yes, she was carrying a BO cylinder, but had no chance to use it until she reached calm water 15 minutes later.

    Luckily, as planned, I deployed my SMB as soon as we hit the water, so the boat could keep track of us while we swam in a shallow channel looking for a pod of dolphins. But the Capt. did not look at the chart and was unaware there was a 60+m drop off at the end of the channel and we got caught in what was effectively an underwater waterfall.

    I experienced the same up/down as my buddy, but on a much smaller scale, because I was able to hold on to the SMB reel and only went up and down over 0-15m. With my spare hand, I was able to depress my OPV and manually to vent gas from the CLs and my nose, and depress the ADV to add fresh gas as depth increased. It is for this reason that I wouldn't ever worry about an O2 spike, because if you are being forced down, you will necessarily need to add dil to fill the CLs to get a breath, probably manually, as most ADVs are not responsive enough in a seriously fast down current. I didn't even think about my wing as I knew it wouldn't help in such a current. Your CL volume is what you should be focused on because you must breathe first and foremost, see previous comments about not panicking just because you are being pushed down, or worrying about the depth, because you have a CCR.

    Also, given this very real possibility of unforeseen strong currents when diving in places like PNG or Indonesia, and because of basic simplicity concerns, I am not in favor of inline ADV shutoffs, and part of the reason I don't like the BOVs I've tried, because they all leaked and required an inline shutoff. Maybe there are newer ones that are better and don't need shutoffs. And when diving with BO that is the same as my onboard, I have my BO gas supply plumbed into the dil reg and leave the valve open, just in case, so all my gas is available to the loop at all times without any fiddling.

    The other salient point about a situation like this is how crucial it is to have physical access to your CLs for the purposes of being able to vent and add gas manually in such a fast moving situation. Things for me would have been way worse if I had back mounted CLs and an OPV I couldn't easily reach. But with my thoughtfully designed Prism OTS CLs, I had only to move my hand a few inches around my chest to dump or add large volumes of gas from the CLs in seconds. That, plus nose venting, gave me more control over my depth changes and lessened my vulnerability to an over pressure lung injury, than if I had BM CLs, no easy access to the OPV and could only vent through my nose.

    The incident in PNG was just a straight down current and took myself and my CCR diving Capt. down to 60+m in a bad tidal down current. There was no sign of the current on the surface, before we jumped, either. It took us 30+ minutes, all our strength climbing up hand over hand and multiple rests to get out of it. We were 2 healthy men, totally spent, sitting on the deck after, thankful we weren't diving OC. Otherwise we would've gone through an AL80 in a few minutes and both been dead.

    IMHO, my CCR kept me calm and ultimately alive in those situations because of the amount of gas available and the time and ability to think things through... -Andy
    Thanks Andy, sounds like you and your partner went through the ringer! Some great thoughts there. I have BMCL's not sure with camera and everything going on I would have reacted fast enough to get to them. I like the early SMB deployment, something I'd definitely do next time. I usually use 2 Litre cylinders and they have been plenty for my diving but given this experience I think I will be upgrading! Really appreciate you sharing your experience given me plenty to think about, though I am hoping never to experience it again I must say.

    Cheers
    Larry


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    Re: Down Currents

    Hi guys,

    So eventually, how do you get escape from a down current (or up current)?
    My thinking was that wing inflation would suffice, but clearly it doesn't. Are you saying that additional SMB inflation would do the trick? Inflating counterlung too?
    Or should we forget about fighting with buoyancy, and rather try to swim away from the current? I have limited understanding of fluid mechanics, but shouldn't the strong current you've described be quite narrow? I believe that's how you've escaped Larry?

    Getting pulled at 60+ msw really scares me. If you've got a hypoxic diluent then fine, but if your dil is air, then you may get close to hyperoxia quite easily. Not to mention possible equalization severe issues you might get (sometimes i find it harder to equalize if i go a bit down after having ascended).
    The alternating up/down currents mentioned by Andy sound quite hell too! Again, equalization can be a challenge, not to mention decompression obligation!!! I guess on locations where such currents are typical, i guess it would be wise to plan no-deco diving.

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    Re: Down Currents

    Nusa Penida just east of Bali is renowned for down currents.The good operators seem to be more able to pick up on the presence of a down current and quickly turn the dive.You put your life at risk trying to save money going with cheap unknown outfits.There are more accidents in Bali related to down currents than is generally let out.
    Remember there are approx.300+ dive operators in Bali.You work out how many are really worth diving with.Do your research as you would for any trip,especially somewhere like Komodo.You're a long way from help,search and rescue if it goes bad.
    While I was doing blue water spearfishing charters off Penida and Lombok I saw whole banana trees floating in the water disappear in whirlpools and never surface.Any escape is a good one from a down current.Good Work.

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    Down Currents

    Quote Originally Posted by Nicool  View Original Post
    Hi guys,

    So eventually, how do you get escape from a down current (or up current)?
    My thinking was that wing inflation would suffice, but clearly it doesn't. Are you saying that additional SMB inflation would do the trick? Inflating counterlung too?
    Or should we forget about fighting with buoyancy, and rather try to swim away from the current? I have limited understanding of fluid mechanics, but shouldn't the strong current you've described be quite narrow? I believe that's how you've escaped Larry?

    Getting pulled at 60+ msw really scares me. If you've got a hypoxic diluent then fine, but if your dil is air, then you may get close to hyperoxia quite easily. Not to mention possible equalization severe issues you might get (sometimes i find it harder to equalize if i go a bit down after having ascended).
    The alternating up/down currents mentioned by Andy sound quite hell too! Again, equalization can be a challenge, not to mention decompression obligation!!! I guess on locations where such currents are typical, i guess it would be wise to plan no-deco diving.
    Hi Nicool, it all happened pretty quickly. My understanding of the underwater topography of the site is that it was a bit like a cliff, so I am guessing it was like an underwater water fall. As to how far I had to swim out, my intention was simply to swim into deeper water as I hoped the current would slow down further away from the island (rightly or wrongly). I was not really conscious of how far I swam out because I was sort of going down and out at the same time. However, I was working pretty hard so it felt like 30 or 40m, but to be honest it may have been way more or way less I couldn't really be sure. I was though more than 400m from shore by the time I came up. Based on Andy's experience I was even luckier than I thought to be able to get out of it. If I'd gone down again for sure I wouldn't have had enough gas to get back up again. I would highly endorse choosing a quality operator. We certainly hadn't picked a cheap option and they came recommended. What my dive buddy and I were not aware of was that our guide had only started diving in the area very recently (last 6-8 weeks) so I guess he just got lost. Btw I didn't mention equalisation. Fortunately for me I can equalise without having to use my hands. If I had to use my hands and the camera and with everything else that was happening, I think I would have had some severe ear problems for sure.
    Cheers Larry


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    Re: Down Currents

    Quote Originally Posted by Nicool  View Original Post
    Hi guys, So eventually, how do you get escape from a down current (or up current)?
    Hi Nicool, it depends. They either eventually carry you into calmer water, or you could try to swim sideways. In Alor, we were in a relatively narrow, shallow channel, so there was nowhere to go. In PNG, we tried to go sideways, but the current appeared to be tidal, meaning wide and massive, and we found no end when moving laterally. The drop off finally started to flatten out, and we were lucky we could find something to hold on to and stop. BTW, I forgot to mention previously, I always wear gloves of some kind when diving in any place that may have strong currents. The Capt. in PNG did not have gloves on and his hands were shredded and he was in much pain for the next week...

    Quote Originally Posted by Nicool  View Original Post
    My thinking was that wing inflation would suffice, but clearly it doesn't. Are you saying that additional SMB inflation would do the trick? Inflating counterlung too? Or should we forget about fighting with buoyancy, and rather try to swim away from the current? I have limited understanding of fluid mechanics, but shouldn't the strong current you've described be quite narrow? I believe that's how you've escaped Larry?
    You almost certainly won't have time to deploy an SMB in the situations I wrote about above. I only had mine up coincidentally, for diver tracking by the boat, not as a hedge against down currents. I wouldn't fight against the current too much. If you can find something to hold on to and stop yourself, great. Otherwise, you will waste gas trying to fight it. The CL's are going to mitigate your depth changes to some degree, but nothing would've helped us in the situations I mentioned. In the worst cases, it should always be about making sure you can maintain enough volume for respiration, and staying calm. In Alor, I watched my 50 lb lift SMB get dragged under 6-8m with me, that's how much force there was sucking us down...

    Quote Originally Posted by Nicool  View Original Post
    Getting pulled at 60+ msw really scares me. If you've got a hypoxic diluent then fine, but if your dil is air, then you may get close to hyperoxia quite easily. Not to mention possible equalization severe issues you might get (sometimes i find it harder to equalize if i go a bit down after having ascended).
    Hopefully, your training and experience will kick in and you will take care of your equalization. I was venting a lot out my nose in the up/down Alor situation, which probably helped with it some. I don't think hyperoxia is as much of a problem, unless you wind up really, really deep, really long. Remember deep air? I think USN divers regularly tolerated 1.8 during hard working dives. That is also why it's important to get stable and calm down your RMV as soon as you can.

    Quote Originally Posted by Nicool  View Original Post
    The alternating up/down currents mentioned by Andy sound quite hell too! Again, equalization can be a challenge, not to mention decompression obligation!!! I guess on locations where such currents are typical, i guess it would be wise to plan no-deco diving.
    Remember, deco obligation is a function of time spent at depth as much as it is what you have in your lungs. I racked up plenty of deco in the PNG situation, but had plenty of time to work it off, since we had a nitrox mixing machine on our backs, and the ascent took a long time; physics + CCR = good . I was equalizing and adding gas with one hand, grabbing for rocks with the other. If your muscle memory and training is good, everything becomes second nature and your survival instinct should do the rest.

    In Alor Indonesia, neither of us were deep for very long each time, it was a yo yo dive profile. So, an over pressure injury was a much greater concern of mine than anything else... -Andy
    Last edited by silent running; 17th September 2014 at 05:24.

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    Down Currents

    Thanks for sharing all this Andy, very interesting and helpful!

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    Re: Down Currents

    Here's a link to a video i took (in 2007 before u/w video cameras were invented ) giving an idea of a typical drift dive.

    We finished with a safety stop all hanging on reef hooks, regs freeflowing if you faced into the current, being circled by two eagle rays. then the biggest manta i've ever seen cruised up alongside us. magic diving, but crazy currents.

  10. #20
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    Re: Down Currents

    Quote Originally Posted by Nicool  View Original Post
    Thanks for sharing all this Andy, very interesting and helpful!
    You are welcome, Nicool. I hope my experiences will give others something to think about. As more CCR divers are certified, more will find themselves in challenging environments. And, nobody gave me any training/advice on how to handle severe current situations, though I think it should at least have been discussed in mod 1. I and my buddies had to find out the hard way... -Andy

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