Surviving currents - do nothing?

[billt4sf]

Yes, the article itself is about surface currents and it may or may not apply to us as divers under the surface.

I am looking for helpful suggestions about how to deal with currents, esp. vertical ones, as I was caught in one several months ago and it was terrifying. I posted my experience in the "Near Misses and Lessons Learned" forum. All the members of my group (about 12 people) were caught unexpectedly in this current, some were very experienced divers, and no one did anything that helped. Fortunately everyone survived without injury.

My own experience was (a) being separated from buddies (b) ear pain, (c) equalize, (d) check depth gauge, all the while overbreathing. Repeat. Once I recall the depth gauge showed 75', once 20', that's all I remember. At no time did I understand what was happening nor why -- until it was over. Others had the presence of mind to inflate their BCDs which did nothing. Hopefully there won't be a next time, as I count myself lucky to survive, or if there is, I will have more presence of mind. I hope.

@Kevrumbo: What do you mean by "finding the downcurrent's edge"? How would that be felt?

Thanks to all for suggestions. Please don't snipe at one another. I wish TS&M was here to give her suggestions. :-(

Bill

 

[Kevrumbo]

. . .

@Kevrumbo: What do you mean by "finding the downcurrent's edge"? How would that be felt?

Thanks to all for suggestions. Please don't snipe at one another. I wish TS&M was here to give her suggestions. :-(

Bill

Similar to the classic way of escaping a rip current: swim orthogonal to the downdraft's pull. The difficult part of this tactic is finding this boundary edge & escaping the downcurrent without overexertion. . .

 

[billt4sf]

Similar to the classic way of escaping a rip current: swim orthogonal to the downdraft's pull. The difficult part of this tactic is finding this boundary edge & escaping the downcurrent without overexertion. . .

Exactly. So how do you find this edge? Or, if what way(s) would it be felt if you were lucky enuf to find it?

- Bill

 

[Kevrumbo]

Exactly. So how do you find this edge? Or, if what way(s) would it be felt if you were lucky enuf to find it?

- Bill

Through Pre-Briefing & Divesite Experience, you anticipate the edge of an approaching downcurrent before ever getting caught in it; For example, especially along the walls of Peleliu (Palau) --when you see your Dive Guide gesturing early to ascend up and away from the wall, do so without delay and stay together with the Guide. There can be a strong down current on the Peleliu Express drift dive flowing over & down to the Southwest near the end of the south point plateau, where the wall starts to quickly descend beyond 18m/60' to well over 39m/130' & deeper. If you're caught in it already, go with the downcurrent until it slackens and then start probing orthogonally for the edge to escape it entirely.

Last time I was there at Peleliu was an early AM special advanced dive charter to see the Black Snapper schooling/spawning, during a full moon (i.e. very strong currents); got caught and swept over the south point plateau in a 3 knot current and decided to ride it out as it it pulled me down to 36 meters --on Eanx32-- and hence the worst case Nitrox Diver's Dilemma & Nightmare: You just inflate your BCD/Wing and do the best you can to slow or maintain depth; try not at all to physically over exert yourself which induces Hypercapnia which increases the chances of Oxygen Toxicity; hope the downcurrent slacks off in time to ascend back above MOD; and deploy your SMB from depth quickly so the boat crew sees you early for eventual pick-up (or else next pick-up point is 1000km to the west in Mindanao Philippines). . .

Again, there are several dynamic variables at play here which will affect the action taken: how much breathing gas left (i.e. Do you have enough to ride out the downdraft at whatever depth it takes you?); your physical exertion & breathing rate (signs/symptoms of Hypercapnia); the strength of the downcurrent; reef topography nearby (can you physically climb a reef wall to escape or are you going down in blue water?); and encroaching on a Nitrox/MOD limit.

 

[Diving Dubai]

A lot of this was discussed in the previous thread Dealing with Currents. However.....

Currents really aren't that scary. The problem arises is that most divers don't experience them that often, and the vast majority of divers are using pretty much all their mental capacity just to dive. Put some stress into the mix and it all goes a bit pear shaped.

Also if your gas supply is near or in the reserve, this also clouds your thought process in how you deal with them. Often people encountering currents have both issues.

I'm a big fan of hanging on, to get some thinking time. If its a big drift, you can choose to go with it, maneuver to see if you can get near the edge, Change depth as currents can weaken or change with different depths, or throw out a DSMB and make a controlled ascent whilst drifting. If your near a wall, head out into the blue (or head for the sand. Chances are the current weakens

Down currents, again hang on. If your shallow chances are the down current will weaken with depth. However if your at 30m then you may not want to go with the option of riding it out. You can try to move horizontally out of it, head away from the wall if you're on one or chuck out a DSMB.


I use an APEX finger spool that is compact and has 50m of line for such emergencies.

The worst, in my view are up currents which can punch you out from depth.

In all cases you just need some time to work things out and maintain your composure. Being comfortable in the normal environment i.e. having all the basics squared away so you have thought capacity, and having reserve gas goes a long way towards this.

I also don't fret about going past 1.6 PPO2 not for a short period. I don't want too, but you can only combat so many things at once.

 

[Darnold9999]

As to how to see current and find the edge one thing not yet mentioned is to watch fish. Their behaviour can tell you a lot about what is happening - before you get in it.

 

[Diving Dubai]

As to how to see current and find the edge one thing not yet mentioned is to watch fish. Their behaviour can tell you a lot about what is happening - before you get in it.

Tongue in cheek...

I see fish hanging stationary with no effort, when I'm being blown right by.. Obviously a ploy to catch out divers

 

[Diving Dubai]

DAN - DEALING WITH DOWN DRAFTS

The following is copied from the DAN site linked above:

Q: Recently I've seen many reports of downdraft currents on various online forums accompanied by debates about the best method for escaping them. Do any of DAN's experts have an opinion or advice?

A: As you will probably appreciate, there is no formal body of research addressing this specific question. The appropriate response and the degree of vigor required will be influenced by the depth, strength and volume of the downdraft, the distance from the eddy line (the edge of the draft), the topography, visibility, risk of entanglement or entrapment, the bulk of the diving equipment worn, the strength, power, buoyancy control, skill, decompression status (or obligation) of the diver and potentially other factors. What seems like a simple question quickly becomes impractical to study in a safe, controlled and still meaningful manner.

Even without quantification of the actual effort required, the question can be addressed conceptually. The priority is maintaining control — particularly vertical control — to avoid serious buoyancy and/or gas-space issues that could make the situation worse. Getting negative, hugging the reef and climbing out rock by rock might be workable if the strength and size of the current flow required it and the topography allowed it. The advantage of this approach is control. The diver is unlikely to have serious shifts in buoyancy or of gas in sensitive spaces (primarily the middle ears and lungs) when control is maintained.

Again, depending on the conditions, swimming perpendicular to the flow could be effective. An advantage of this may be a reasonable degree of control, with minimal need for fast changes in buoyant state or risk to sensitive gas spaces. Choosing to increase buoyancy probably represents the greatest risk of all. While it may be necessary in extreme situations, it is also possible that it could result in an overcorrection and the subsequent hazards of an uncontrolled ascent, the latter resulting in an elevated risk of barotrauma and decompression illness.

My fundamental recommendation is that divers think in advance and be prepared with a continuum of responses from which to choose and, when appropriate, to shift between. The progression of the graded response would be as follows: a mild downdraft could be ignored; a little more strength would prompt horizontal swimming to move out of the affected zone (with minimal or no addition of air to the BCD); even more strength or an uncomfortably large downdraft flow zone would prompt grabbing the wall for stability and, possibly, climbing out. A minor amount of gas might be added to the BCD at the hanging-onto-the-wall point, but not as a primary part of the solution. Adding too much positive buoyancy could create a situation more dangerous than the initial hazard. It could pull the diver off the wall, precipitate a runaway ascent or make what could otherwise be a mild case of entanglement extremely problematic.
Mental practice is an important way to improve skills and responsiveness. A critical part of this effort is to remember that every event has its own idiosyncrasies. Having multiple options and the physical skills and calm demeanor to employ them in a thoughtful, progressive manner will provide the best protection.
—Neal W. Pollock, Ph.D.

 

[Eric Sedletzky]

I've never been caught in a down current underwater, only surface currents and some of them were very strong.
I've thought about down currents though, and hypothetically thought of ways to potentially deal with them. I've had friends that got caught in down currents, one as a matter of fact on a vacation to Palau with his wife.

My ideas to deal with them would first be to try and assess what is happening by trying to find a fixed object like a wall or an anchor line or whatever. I'm sure sudden pressure on the ears would be an indication of rapidly changing depth. Then I would look at my depth gauge and see what's going on since to me that would really be the only way to actually see where your at.
In my way of doing things I automatically pick gear that is as streamlined as possible with minimal clutter. I like minimalist profiled gear like back pack style plates and very small wings, all hoses kept tight against the body, etc. I don't like conventional gear precisely for the reasons that they are too cluttered and create a lot of drag. This could be a real drag in currents (pun intended). I would also probably be using freediving fins.

I would address the flow of water the same as when cruising normally, I would orient my body towards the oncoming direction of flow meaning that in a downcurrent I would be verticle making as small a profile towards to flow. This is where to me trying to maintain a perfect sky diver position like many advocate "perfect trim" would be counter productive by making a larger surface area for water to push against.
Not only would I be verticle but I would be finning slowly and as efficiently as possible which with freediving fins can be very easy and produce a great amount of thrust. And also it would be very important to not over work, the CO2 debacle is very real!
The whole time I would be following my depth gauge since that would be the only indication if I'm winning or not. And at the same time I would be making an angled path trying to find the edge of the draft. I don't think I would just lay there and let the current spit me out somewhere, not that I would have a choice, but I'd like to think that I at least made somewhat of a valiant effort to extricate myself from the situation.
This is about all I could think to do. I don't know how "correct" it is according to the downdraft experts but it's what I would do, or attempt to do anyway in theory.

I guess the best way to avoid downdrafts is not to go looking for them, i.e. avoid prone areas on days when conditions might have a track record of being bad.

 

[livinthedream]

Here is something I recently wrote for my shop in Palau. This is my first attempt at writing:

Down-wellings or down-currents occur here mainly along our deeper plateaus, Siaes Corner, Shark City, Blue Corner, New Drop Off and Peleliu (Cut, Corner and Express). They occur because the current doesn’t run parallel to the plateau but at an intersecting angle. When the water hits the wall it splits creating an upwelling of water pushing up, then over the top of the plateau. This upwelling is what makes utilizing reef hooks such a thrilling ride. With your reef hook firmly set in a rock or DEAD coral we soar in the upwelling like a kite in the wind watching marine life ride out these shifting currents live in HD. When we unhook and ride the current across the plateau is when we are most at risk for a down-welling or down current. This is caused because the water no longer has a wall to push against and now rushes across the plateau, when it reaches the other side it creates a waterfall effect as it runs over the edge. 95% of the time diving in Palau you will never experience these down-currents, these generally only occur when the tide is extremely strong. But it is still something we should be prepared for.

Getting caught in a strong down current can be a frightening experience as a precaution here are a few steps you can take to avoid them:
Follow your guide- You've trusted us so far and we dive these sites and conditions constantly so follow our directions. If we say come up it’s time to come up, not time to take one last picture or follow that Napoleon Wrasse. We’re here to make sure you continue to enjoy your vacation, if we are asking you to come up, be sure there is a good reason.

Ascend Early - In strong currents begin your ascent so that we reach safety stop depth while crossing the plateau well before the edge. This will bring you above the force of the down-welling.

How to recognize a down-current:
Pay attention to your computer – Depth changes can occur rapidly. 10m to 30m in 5 seconds can occur. Decompression obligations can easily become a factor.

Pay attention to your ears – Due to the rapid change in depth our ears can be our best guide to identifying that we are caught in a down-current. Equalize often and quickly to avoid trauma to your ears.

Watch your bubbles – Down currents can very disorienting, exhaled bubbles will circle around you and be pulled down.

Watch the fish – If the fish are along the wall, vertical in orientation and swimming hard just to keep position this a sure fire give away of a down-current, if a fish can’t swim against it do you really think you can?


If you do get caught in a down-current remember these steps:
Get away from the wall – yes swimming into the deep blue can be intimidating, but the further you get from the wall/plateau, the lesser the grasp it has on you. Refer back to the waterfall analogy to escape the waterfall you wouldn’t go stand underneath it would you? Once clear of the pull deploy your DSMB (Delayed Surface Marker Buoy) and begin a normal ascent. You may find yourself needing to make a decompression stop due to returning to depth at the end of the dive.

Breathe and Relax – Sounds difficult and it is, however maintaining or resuming regular deep breathing is the most important thing one can do in an emergency. It helps clear the mind and opens us up to problem solving solutions instead of instinctual reactions.

Inflate your BCD - This is something that should be done in emergencies only. If swimming away from the wall isn’t working on it’s own you may need to inflate your BCD to break free. If this is so keep the inflator in your hand and be prepared to vent air quickly, as once free of the down-welling an inflated BCD will cause a runaway ascent.