Silt Out - Wreck Danger! A graphic video demonstration.

[DA Aquamaster]

I am firm believer in training in real conditions. You can simulate a silt out all you want, but the divers being trained still know that if it all goes to sh*t the instructor will just turn the lights back on or un cover the mask. Take that same diver into a reasonably well controlled but still real environment (a simple passage where they won't get lost and where things will clear reasonably fast) and it has an entirely different psychological effect because it's (more) real and the instructor is not going to just be able to turn off the silt.

In that regard I am always somewhat mortifed when cave divers report he or she was in his or her first silt out. In my opinion, if you have not been in a real silt out, you have not earned the card yet. But then that's from a mostly Florida cave perspective with fine silts and clays that are easy to stir and that can be very persistent and hang for hours rather than minutes in low flow passages.

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Some diver may view the video and be tempted to think that they'd never screw it up and blow the viz. It's easier than it looks, and in some cases in seldom accessed areas of wrecks or caves, your bubbles will percolate stuff off the ceiling and blow the viz. And even if your team is indeed perfect, the team coming in behind you may not be, and you'll still have to exit through their mess - a mess that will have by then spread through multiple compartments or killed the viz over a much larger distance.

 

[Akimbo]

I agree with DA Aquamaster. Black mask training (faceplate/lens painted black) is psychologically nothing like training in ink-black water. Burning up a full tank in black water is a good exercise and should be experienced by every diver at least once. It changes your perspective and dive planning on every dive, no matter how clear the water is that day.

 

[TSandM]

It's easier than it looks, and in some cases in seldom accessed areas of wrecks or caves, your bubbles will percolate stuff off the ceiling and blow the viz. And even if your team is indeed perfect, the team coming in behind you may not be, and you'll still have to exit through their mess - a mess that will have by then spread through multiple compartments or killed the viz over a much larger distance.

I have a video from the trip we just completed, showing some serious percolation as a result of penetrating a passage that hadn't been dived in 7 years. As soon as I learn how to edit it, I'll add it to this thread.

I wonder how many cave instructors create deliberate siltouts? None of my four did. It was all "lights-out" stuff. I think keeping student control in a real siltout would be difficult. The fellow who took us through that exercise had to have a great deal of trust in our ability to keep ourselves together.

 

[ElGaucho]

My full cave included a real silt out. This was a Mexican cave. It still was done in a controlled passage where the silty portion was very localized which allowed to swim through it easily. The objective was to see a silt out an understand how silt behaves. Not so much not to see anything at all. I enjoyed it. Also when doing lost line at the end, it got pretty silted out. Again it was way to swim out of the silted portion. This was with two students an instructor and an ass instructor. So it felt very safe.

 

[Doc Harry]

Wow.

Extremely poor finning technique - anyone suprised that there was silt out?

Extremely poor reel technique and utilization - that line wouldn't have helped much in that silt out.

Overhead penetrations with a single tank - icing on the cake!

Or...

Is this really the trailer for an new Stephen King horror movie?

 

[ElGaucho]

Some diver may view the video and be tempted to think that they'd never screw it up and blow the viz. It's easier than it looks, and in some cases in seldom accessed areas of wrecks or caves, your bubbles will percolate stuff off the ceiling and blow the viz. And even if your team is indeed perfect, the team coming in behind you may not be, and you'll still have to exit through their mess - a mess that will have by then spread through multiple compartments or killed the viz over a much larger distance.

And as the cave diving mantra goes: everything will go to **** at the same time, or in a more polite manner "the incident pit" (one problem brings another problem, brings another problem, etc). Silt outs will probably be accompanied by another factor. You dropped the reel, it fell to the ground, in trying to grab it it starts silting out, but since you are worried about the reel, you don't really notice it, etc, etc. Or you loose buoyancy for a miriad of possible reasons that distract you. It's much easier to fall into the incident pit than it looks on paper. And silt outs can very well be an integral part of the incident pit. That's why it's nice to experience them in a controlled situation. Lights out, blacked out masks, no masks, they all work fine and dandy. But experiencing one or two silt outs once you are close to the end of a full cave course really adds to keeping cool that lousy day you start falling in the incident pit, some years later inside a wreck, a cave, or just doing a dive and loosing viz for any reason. And as many cave instructors will tell you, just close your eyes, and turn off that portion of the brain that will still try to figure out what's that minuscule portion you can still see. Trust the line, trust you instinct and loose the sight if it's not useful. It will just make you feel anxious and confuse your feeble brain.

 

[Belmont]

The first dive at Jailhouse is an "Eye opener".
You start with a silt out in open water.

 

[tracydr]

Andy, I'm with you. You can describe problems until you are blue in the face, but letting divers have a controlled experience of the trouble they can get into teaches far faster and more effectively.

A couple of years ago, I was taken through a cave passage by a friend, who had told us we WOULD silt it out, and did we want to have an experience of zero viz? (Friend is a cave instructor, and we were reasonably experienced cave tourists by that time, but had only done lights-out drills in class, and never been in zero viz.) We said we thought it would be a good thing to learn, so we did it. It was only about maybe 50 feet of passage, and I was convinced I could swim it clean, but I had little understanding of Florida sediments. Our friend was right; it was true, can't-read-gauges-pressed-to-mask zero viz on the way out. It was very interesting and instructive, and left me with a great deal more caution about trying smaller passage in Florida -- and I'm talking stuff that wouldn't even make me stop and THINK in Mexico.

There is understanding at the intellectual level, and understanding at the visceral level, and they are different. I applaud you, Andy, for making these things clear to your students. (BTW, the wreck class I took, years ago, didn't even involve entering a wreck, and I came away from with convinced I had no business doing so )

It's terrifying how disorienting zero vis can be. I have experienced it a few times in our local lake. It caused me to feel very uneasy the first time it happened. I couldn't even read my computer to judge my depth. Now that I've experienced it a few times, I have a lot more respect for the dangers in a cave from zero vis.

 

[Rhone Man]

Thanks for posting. Reason #422 why I love SB.

By the grace of God, I have never been a real silt-out situation, but I remember when I was taking some technical courses speaking to some vastly experience Canadian wreck divers who were talking me through their silt-out experiences. They were extremely calm how they handled it, which I suppose is why they were able to tell me about it years later.

 

[gcarter]

I deliberately silted myself in about 12 feet of water off the end of a friends dock so I would know what it is like. It is quite surreal. Not at all like being in the dark (this was a bright day at the lake) but still being blind. Not being able to see my gauges or computer directly in front of my face. Light useless.

It was good to have experienced it in a calm state, as it has helped me keep low vis conditions in perspective, and to recognize what is happening when the silt starts flying. I have no interest in wreck penetration or caves, but it is not just those dives where silt happens. Even in OW you need to maintain your calm, your orientation, and find your way home.