What is proper procedure for downcurrent

[SDAnderson]

What a person needs to do is learn how to "Ferry" across current and keep your fingers off the inflator. It doesn't matter what direction the current is going in but you have to be able to identify what it's doing first. It takes training and practice but it works.

Training and practice acquired how?

 

[mattengstrom]

...
And do not drop your weights!

Gary D.

That's been said a few times by different people in this thread, but as the Galapagos case shows (to me, at least) this is NOT an absolute statement. If I'm getting deep, AND my BC is already inflated, AND the downcurrent is not showing any other signs of abating, I'm going to start to drop weight.

Yes, I'll agree that this puts you at risk of an uncontrolled ascent, which in turn puts you at risk of taking a DCS hit.

NOT dropping weight though puts you at risk of staying on that downward-heading train, with the next stop being "drowning" and a write-up in ScubaDiving's Lessons Learned column.

I'll take my chances with DCS. After, of course, I've tried everything else that's been mentioned.

Not trying to start a fight - just trying to make the point that dropping weight should be considered as a last-resort option. This is one of the best threads that we've had here in a long time.

 

[Web Monkey]

"Shooting" a lift bag's not an option, so don't bother trying. I do reccommend carrying a "sausage" (6-10', not the little 4') and a small reel (spool).

Why is shooting a lift bag not an option?

A 10' Personal Market Buoy (OMS, I beleive) is good for about 90 pounds of lift. Between that and an inflated BC, I'd find it hard to imagine that you couldn't stop going down.

Terry

 

[Charlie99]

A 10' Personal Market Buoy (OMS, I beleive) is good for about 90 pounds of lift. Between that and an inflated BC, I'd find it hard to imagine that you couldn't stop going down.

I must have better imagination.

Your marker buoy has a certain rate of ascent when you shoot it at depth. If the vertical component of the downcurrent is faster than that ascent rate, then your marker buoy goes down (relative to the surface), not up. I don't know if this is probable, but is imaginable.

On a more practical basis, if the downwelling is caused by current hitting a wall, the high speed downcurrent is probably not too wide and you could probably swim out of it faster than the tiime it takes to shoot a bag.

 

[Gary D.]

That's been said a few times by different people in this thread, but as the Galapagos case shows (to me, at least) this is NOT an absolute statement. If I'm getting deep, AND my BC is already inflated, AND the downcurrent is not showing any other signs of abating, I'm going to start to drop weight.

Yes, I'll agree that this puts you at risk of an uncontrolled ascent, which in turn puts you at risk of taking a DCS hit.

NOT dropping weight though puts you at risk of staying on that downward-heading train, with the next stop being "drowning" and a write-up in ScubaDiving's Lessons Learned column.

I'll take my chances with DCS. After, of course, I've tried everything else that's been mentioned.

Not trying to start a fight - just trying to make the point that dropping weight should be considered as a last-resort option. This is one of the best threads that we've had here in a long time.

Not much is absolute and everything has variables. What I meant about dumping your weights would be as a last resort.
Some people might want to dump to soon in this type of situtation.

Every current is different, as is every diver. You have to be flexible enough to react with the current as it changes. Ocean currents are subject to a lot of changes where lakes and rivers are more constant.

In rivers there are several currents not just the downstream horizontal one everyone is familiar with. Depending on the size of the river, flow, shape and depth you can have about every current imaginable. The Helical current is by far the most fun.

There is no fight here just a good discussion.

I think if you could see the video’s you would have a better idea. Rick and I are planning on getting together in the near future. I’ll let him see the videos and see if he can explain it any different than I have.

As far as training that is available I know it’s there for PSD’s but I don’t know where else.

Gary D.

 

[ArcticDiver]

The current we have been refering to was a very unpredictable go everywhere but up current. It was two currents that came together with one rolling over the other. On my original video I got a quick shot of the surface line in the distance.

We were down for a while when it appears to have come across the bottom headed out to sea. When it hit the reef it went up and then sharply down where we got caught. On the way up I got another shot of the line from below.

If I remember right everyone who inflated their BC's had problems over and above everyone elses.

What a person needs to do is learn how to "Ferry" across current and keep your fingers off the inflator. It doesn't matter what direction the current is going in but you have to be able to identify what it's doing first. It takes training and practice but it works.

Your right about various size object moving at the same rate along the current. But the object is to counteract the current and swim in a direction other than the direction the current wants you to go. In that case a very small change in size, streamlining and body position make a big difference in the forces applied.

And do not drop your weights!

Gary D.

Of course the whole purpose of this discussion is to give folks an idea of how to go where they want to rather than where the current is taking them. That is why I used the vector analysis example. It gives any diver a structure to build their decision making on.

Rarely though will you find a strong current that only has a single component. I venture to say many will have multiple current vectors. The "magic" if there is any is for the diver to keep cool and figure out what the vectors are. In your example Gary you had one of those multiple current situations. It is really hard for a person to figure things out while being tumbled about let alone keep cool enough for a decision.

For example in my first experience I was able to fin out of the problem. In the second finning and fully inflated BC didn't help. The current dissapated before I got to the drop weights stage. Thankfully!

The only point I would make again and make it strongly is that if a diver is in a vertical current where finning and a fully inflated BC have been given a chance to work but aren't solving the problem: Drop Your Weights! You May end up with DCS later. But a possible problem later is much better than a for sure problem now.

 

[Hoppy]

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 ?

 

[H2Andy]

yes, if you exceed your ata max.

but remember, NAVY tables allow you to dive with 1.6/1.8 limits, so chances of anything happening if you exceed 1.4/1.6 (PADI limits) are minimal.

the problem is, if anything is going to happen, it's going to happen pretty fast, so...
yeah.. you'd be screwed imo

 

[SDAnderson]

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

Same thing that would happen if you're diving air and you hit your MOD, just a little sooner.

 

[Charlie99]

NOAA exceptional exposure limit is 30 minutes at 2.0ppO2. For EAN32, that's 173'.

In most cases, running out of gas is the greater danger.

added: http://www.diversalertnetwork.org/medical/articles/article.asp?articleid=35 . Exceptional exposure table is at the bottom of the article, along with a comment about the effect of 5 minute exposure to 100% O2 2.5ppO2 ---- apparently no observable effect on the allowable exposure time at 20' (1.6ppO2).