What is proper procedure for downcurrent

[mars2u]

I posted this in June '03 during my trip to Palau. You can search for the thread to see replies...but here's the story

:54:

Palau undercurrent close call...

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Just as an FYI...we learn and hopefully we live. You can see pics of the typhoon conditions (later turned into typhoon Chen) that we encountered on my web site.

On the second day it was decided that we dive the "Buoy #6 wreck" which is a WWII sub chaser that was sunk located in the Molarei channel.

Water temperature 84°F/29°C Visibility 20ft/7m at best

Air temperature 84°F/29°C

Dive time: 19 minutes



We had our dive briefing before the dive as usual and had discussed the dive. I was paired up with Kristen who was with her parents Doug and Deb on our trip. We took the chaseboats out to the site and began our descent together. As we descended lower and lower I noticed that those ahead of me were moving at an awfully quick pace. The visibility was poor anyway and it was difficult to discern the divers from one another. I tried to concentrate on Kristen since she was wearing a blue bandanna on this dive as was I. The current got quicker...I'm at 77 ft. Approaching the wreck...there's Kristen just behind me... oh no...the current is picking up, it's racing...I just passed the wreck in about 3 seconds...but it's supposedly 100 ft. long. TURN DAMIR TURN!!! I'm kicking, against the current, I can't see Kristen...damn. Everyone is scrambling. Trying to get control but the current is too strong. Couples are grabbing ahold of each other at various pieces of their gear trying to keep together. Some are just blown in different directions in a split second while others are holding onto each other to keep from getting seperated in the pea soup of Palau. I look to my left and Lee is kicking like a madman....then SLAM!!! I just took out a 3 ft. piece of a coral fan...I'm tumbling and I realize another BIG coral rock is approaching fast...I need to keep an eye out for what's coming at me since my finning against the current is not doing much. I look around, I'm alone, I see a patch of sand and I'm about 10 feet from the bottom. I kick as hard as I can and dig my knife into the sand. DIG DAMN IT DIG!!! The knife is cutting through the sand bottom like melted butter leaving a 10 ft. trail, I try again using my left hand also to dig with my fingers in the sand...it's not catching, finally and after the 3rd attempt I finally stop and am holding on with both hands on my knife. I'm reflecting for what seems like a while trying to catch my breath and slow down my breathing. I'm thinking about Kristen, how her Mom and Dad are doing...(probably having the dive of their life and wanting to kill me for losing their daughter). I'm staring at the sand bewildered and trying to figure out where to look for Kristen, all the while looking around for any sign of my group. I realize I taste alot of water in my mouth...oh no my reg is getting flooded from the current. I look up and there's Andre (the dive master) with Kristen next to him...thank God, at least he's been watching her. I'm finally resting and catching my breath when he signals me to come up to them.

I release, store my knife, but the current has already whisked them away and I can't even see their shadows. I adjust my venturi...still sucking water on my Legend LX. Damn...I'm beat and I look at my watch to realize were only 15 minutes into the dive and it has just seemed like it's rushed by. I look around and there's nothing...it's pea soup and the visibility is getting even worse now. I'm still moving at an extremely quick pace and decide to abort the dive (about time). I'm at about 15 feet when I see Gat (the other Dive Master) kicking like a madman and approaching me from behind. He looks at me and crosses his hands in a "X" symbol telling me to abort the dive. I'm thinking..."Already there Gat, 1 minute left on the safety stop", sausage deployed, and give him the O.K. He then leaves and kicks across the current hoping to find someone else. I again am all alone. I finish my safety stop and as I'm surfacing think to myself...I hope no one got hurt or worse...

At the surface I look around and I see some heads bobbing about 200 meters at my 7 o'clock... another couple of heads about 100 meters at my 9 o'clock. "God, I hope Kristen is O.K." The chaseboat comes around and it's the other groups (we were split into 2 dive groups). I signal the operator that I'm O.K. and he drives off to look for anyone in trouble. My boat comes to get me and there's Pam and Dave (another couple)...Pam's shook up...really bad.

She begins to give her account of the events and says that at one point her computer showed 24 feet (if memory serves me) and the next second shot down to 56 ft. One word pops into my mind... undercurrent. It was so bad that the bubbles were whipping around them and she kept looking down thinking that someone was beneath them. After reviewing my dive computer...she was right. My entire dive profile was strewn with fast ascent warning's as we were getting shot up and down.

Andre (the divemaster) probably got it worst. It seems that he was approaching the back of the wreck and was trying to go above it when the current slammed him down causing multiple scrapes over his legs. He was hurting for a while. Thank God it wasn't fire coral.

After getting back on the Big Blue, we all reflected and we still had a night dive to go. A handful (I believe 5) including myself, Kristen and her Dad decided to go. We decided to do the "Helmet Wreck" which was right next to the Big Blue. I had to get the monkey off my back although I was still a little shaken.

I still feel guilty about losing my dive buddy Kristen. She and her parents as well as the others assured me there was nothing I could do and in retrospect they are probably right. However, I am the type of diver that likes to sit back in the pack and enjoy my dive as well as keep an eye out for everyone. It's just my nature.

In retrospect, yes the trip could have been much better and there were some hairy moments, but we still got to see things we've never seen before. I think we are all much better divers for the experience and maybe even better people. I know I made some close friends.

 

[OE2X]

My buddy and I were casually doing a drift in 3 knots of current on a wall. We were at about 50 feet with the feeling like we were on the Orient express since the scenery was whipping by us. After about 10 minutes we found ourselves on the downward elevator going towards the deep blue. Computers were going off and we were filling our BC's as fast we could. At about 140' we saw a large outcropping of corral approaching rapidly. We moved away from the wall just enough to clear it and as soon as we possibly could we finned our way behind and under it. Here we found ourselves out of the downwelling and dumped our nearly full BC's while hanging on to the coral. We were able to find a channel to work our way back up the wall. At about 100' the down welling had subsided and we were then able to ascend to about 40' where we found no more than a knot of current. Did a saftey stop at 30' and 15' just to be extra safe and then surfaced.
Since then when ever I do a wall dive, I always keep an eye out for an outcropping to find shelter beneath or behind.

 

[Capnsnott]

I have a story, but not much more advise other that what I did.
I was in Nassau, NW side of the island. We were down about 70' and a current started pushing us back toward the shelf edge (2500' drop). The leader was staying about 5' above the bottom, I was doing fine swimming into it untill one of my fins broke. I had rentals because I left mine at home for restrictive travel reasons. The fin actually busted at the ribs. I was carried backwards pretty fast at that point. I managed to swim sideways and ascend at the same time. The current still pushed me, but the side swimming alowed me to change vertical position within the current. It wasn't stong enough to send me 100' down in a few secounds, but still pretty harsh.

 

[ArcticDiver]

if you dive Nitrox and this happens, what the hell happens when you hit your floor ?

Do I assume you are in BIG trouble ? CNS hit etc ? Would seem to be that way yeah ?

Time is one of the critical factors in determining whether or not a diver will suffer a "hit" from exceeding the calculated depth limit. Very little in the human body happens instantaneously. So there isn't really a solid "floor". It is more like a time factored water continuum.

Other factors have been mentioned in other posts so I'll not repeat. One though has not. That is physical fitness. A general rule is that the more fit a person is the less they have to exert themselves to accomplish a task and the less breathing gas they will use in the process. Obviously, the less gas you use the longer the time delay before that gas affects the body. On the other hand if you are not fit your actual MOD regardless of tables might be much shallower than calculated.

So, in my view, when you get caught in a downwelling don't waste time and effort worrying about a cns hit.

Hmmm, stray thought, wonder if the folks who disappeared in the whirlpool off New Zealand a few years ago were diving a mixed gas? If so, I suppose a cns hit would have been considered merciful.

 

[H2Andy]

Time is one of the critical factors in determining whether or not a diver will suffer a "hit" from exceeding the calculated depth limit. Very little in the human body happens instantaneously. So there isn't really a solid "floor". It is more like a time factored water continuum.

does this apply to an oxygen toxicity seizure?

my understanding is that they can happen rather quickly, with
no warning.

 

[ArcticDiver]

does this apply to an oxygen toxicity seizure?

my understanding is that they can happen rather quickly, with
no warning.

The original post seemed to directly imply that when the MOD was reached a chemical "switch" was thrown and the diver convulsed and died. My intent is merely to present the idea that oxygen toxicity has to take some time. It is more like a rheostat than a switch. Now that rheostat may be spun rather quickly depending on the factors I mentioned. But the effect isn't instantaneous.

But, oxygen toxicity is only one of the threats posed by the down current. My basic point was to not waste time worrying about that and instead spend the time and energy getting out of the situation. Personally, I'd rather be on EAN in this circumstance because it would lower my risk of DCS during the recovery phase of this evolution.

 

[Charlie99]

does this apply to an oxygen toxicity seizure?

my understanding is that they can happen rather quickly, with
no warning.

While going from no symptom to full seizure can happen quickly, to quote the DAN I linked above: "Oxygen toxicity is a time duration phenomenon: that is, both time and partial pressure play a role."

More crudely put, there isn't a certain "trigger level" of ppO2 above which CNS immediately occurs, and below which there isn't a problem. Many divers seem to think that 1.4 (or 1.6) ata ppO2 is some such magic number. It isn't. Oxtox risk is a nonlinear function of ppO2 AND time duration of exposure.

Good article on oxtox

 

[H2Andy]

excellent guys, thank you

 

[hantzu701]

I just skimmed the last four pages:

I remember my first downcurrent - 95ft to 110ft in two breaths. We were following a sloping wall. We didn't even realize it until our computers started beeping.

Are we in agreement that the 1st course of action to get out of the current is to get closer to the coral?

Adv: You can grab coral, stay put and assess what ur next steps need to be.
Dis: Current can rip ur reg, mask, etc.

Hantzu

 

[SDAnderson]

Are we in agreement that the 1st course of action to get out of the current is to get closer to the coral?

Adv: You can grab coral, stay put and assess what ur next steps need to be.
Dis: Current can rip ur reg, mask, etc.

I've only got limited experience at this, but this wouldn't be my first choice. This method imposes a pretty high risk of damaging myself or my gear (or the environment) and often the closest "out" door is in exactly the opposite direction - the faster you get away from the wall or the channel floor, the sooner you'll be out of the current or at least in a place that you can be picked up.