What is proper procedure for downcurrent

[Snowbear]

Today is Saturday, But not That Saturday. That Saturday is the 20th.

Are we still on for That Sunday?

Yep, still on for THAT Sunday

 

[ArcticDiver]

Super!

Now just to keep the snake from biting

 

[caymaniac]

I agree with those that say "fin & inflate", I have not had allot of experience, but some.
While diving in the Red Sea (Egypt), we were briefed on how we would all dive off the boat together (6 divers), the current would take us near a wall where we would see some really large sea fans at around the 60 ft. level, then after passing the fans the current would take us to a cut in the reef wall where we would finish our dive. "It all sounds so good on paper!".
After jumping off the boat together and we proceeded to get some depth, at approx. 20 feet my wife and I tried to stop our descent. It was to no avail, we continued to go down and we
were picking up speed. We both started finning....hard, it didn't seem enough so we inflated our BCs, at 124ft. we finally seemed to gain a bit, we lost sight of the rest of our group. We ascended to around 20 ft. where we were trying to do a major BC dump. Now we were out of the down current and onto a side thrusting current. We were first just happy to be out of that down current, then we were not so happy when we didn't see any other divers. Meanwhile, the current had a pretty good sideways hold on us and we were approaching a wall...fast. In sight soon were the large sea fans and then on the otherside of the fan wall were the rest of the group. Now, this all happened pretty fast and was quite scary.
Do you think we had time to take our weight belts off and try taking one weight off at a time to see if we would start to rise?
NOT! "It all sounds so good on paper!"

Dive Safe,
Caymaniac

:54:

 

[espenskogen]

Not exactly. I said:

I didn't mean to imply that 3 knots is the starting point for trouble, I picked that rate because it more or less equals an easily grasped 100 fpm.

This is not true - 1 knot equates to roughly 100 fpm - 3 knots equals 303.7 fpm

That's pretty deep, pretty fast.

 

[espenskogen]

This has been fun to watch, and i will throw my hat into the ring as well with a few points.

1) As you descend, that 45# lift wing, will have less lift as the volume reduces, depending on how quickly you go down will be proportional to the volume reduction, so the constant force is not that. If you have more lift than the current (+5 in last case) then the the force will be constant if you BC/Wing is full, if you are going down, you may start at -5# (in last case) due to the current being stronger than the lift, but that amount will increase -6#, -7# etc as you go down.

True, if you don't ensure that your wing remains fully inflated throughout your runaway decent.

But if you compensate for the compression of the gas in your wing, the lift will remain constant.

2) The force exerted on you by the current is a drag from you profile in the water, so the more surface area you have the more drag, the more force pushing you down as you inflate your BC/Wing. The difference may only be marginal from full to empty though depending on your wing size, 45# + body profile, larger than 27# + body profile.

True, but this would only have an effect through the acceleration phase - Once you're accellerated to the speed of the current (Which, due to the density of the water, happens pretty damned fast), the increased drag by your bc will easily be offset against the lift of the bc. In the instance of you filling your wing with something not boyant, say water for example, the increased volume of the bc would give you increased drag, which would make it more difficult to fight the current, but it wouldn't make you go any faster, once you've been caught, than otherwise. Therefore, the only sensible option is to increase your boyancy by inflating every air space you have available to stop the decent (Bearing in mind that air gets poisonous at between 60 and 100 meters (Depending on your CNS o2 Exposure)) and then be pretty quick at dumping air back to neutral boyancy again.

 

[aabond]

I'm glad you guys want to continue talking about this, but this thread has been dead for almost two years.

 

[Damselfish]

still good discussion & info, why have it on a different thread.

 

[Bruciebabe]

I have had loads of fun in downcurrents. As long as you are correctly weighted (rare among divers) and have enough lift they are just a part of the normal skillset.
The first time I encountered really significant downcurrents was in the Red Sea at the Brothers. Here the game was given away by all the fish pointing up. So it was simply a matter of keeping an eye on the computer and using the buttons on the end of the inflator hose to manage it.
Then there was diving the deep coral outcrops in the Maldive atol chanels in January. Here you jump off the diveboat a few hundred metres up current of the site and then swim down really fast to hit a small target. Often you daren't move your head from straight into the current because it will take your mask off. When you let go and start your ascent you are in a washing machine. Once I was about to pop the blob at 5 metres when the wife disappeared downwards. As we were recently married I followed her down till she realised and pushed her power inflate at about 20 metres. Her descent only took a few seconds and she is much better at looking at her instruments now.
Then there was Manado. I have over a hundred dives there. You can do adrenaline drifts on the tide between the islands. The added bonus is that many millions of tons of water are pouring off the vast frindging reefs onto your head. By now the wife had learned and she must have enjoyed the added complication of not being able to see me a metre away due to our bubbles not going up and just sitting in the water creating a dense fog. You almost felt like you could take your reg out and breathe.
Just recently I was in Puerto Galera and did the Canyons when the ebb tide was at its fastest. There were no other dive groups trying this but as we were all instructors we had a slight advantage. Getting into Cayon #2 was hard physical work but worth it because it was completely filled with big fish. Hardly any room for us. When we left the seafloor falls away quickly. In the huge downcurrent people often think they are ascending when they are actually going down because they are using the seabed as a reference. The only answer, as always, was to use the computer and the power inflate button to manage this most enjoyable ride.
One of the problems with downcurrents is the PADI doctrine of ascending with neutral buoyancy. This makes people very averse to hitting their power inflate on the way up even if this is what is needed to stay neautral.

 

[Foo]

Once I was about to pop the blob at 5 metres when the wife disappeared downwards. As we were recently married I followed her down till she realised and pushed her power inflate at about 20 metres.

LOL, Brucie... if she had been an older model, would you have just let her plow downwards alone?
Foo

 

[ExactFunctor]

My newbie question is...how in the world do you equalize when you're being dragged down to 210 feet, as one diver was in the thread?