Emergency Exit in Caves and Wrecks

[VeniVidi]

Dear wreck divers,

This question is basically addressed to anyone that obtain cave as well as wreck diving experience alike. One can read often enough that wrecks and caves are different diciplines due to their different quality of environment. I am intrigued in what is common and what is different, though. For larger wreck penetrations, also lines and directional markers are laid, the propulsion techniques must be likewise highly developed as it is in caving and more of the like.

My question: how does the emergency exit compare with cave diving, especially when "touch-contacting" in zero-viz? If it is the same, then line-techniques are similar to those in the cave zone. But is this possible? How about line trapping? How do/would you manage this?

I do not want to evoke answers that are manageable by common sense or refer to basic overhead environment skills (although my question might fall in this category). I envision a delicate wreck environment to become an additional hazard and, in a worst case scenario, would collapse when divers bumped into the structure while no-viz-exiting.

 

[Dive-aholic]

Caves have permanent lines (gold line) already in place. Wrecks don't. This could have an effect on the exit and line trapping. Unless the gold line breaks in a cave, it seems like it would be easier to exit a cave. Wreck lines are placed by the diver so it all depends on the skill of the diver. The difference would be in the amount of penetration. Wreck penetrations are usually much shorter than cave penetrations, as far as distance is concerned.

 

[DA Aquamaster]

One of the biggest differences in the presence of sharp surfaces in a wreck that can cut a line as well as wires, cables and debris that can cause entanglement problems in low visibility. You want to be careful when laying the line to tie it off so as to avoid chafing of the line and to lay the line whenever possible in areas where you will not encounter entanglement hazards if you are exiting in low visibility.

Also where cave divers will use a smaller diameter line, perhaps #24 (.073" dia) for it's greater spool capacity, wreck divers will use a heavier line such as #48 (.098" dia) or even 1/8" (.125" dia) for the additional abrasion resistance it provides.

The use of lines in a wreck is not universal. Traditional wreck divers used progressive penetration techniques to learn their way around inside a wreck over the course of several dives. The feeling was that safety came from familiarity with the wreck and could not be short cutted. The use off a pentration line was a cave technique adapted to wreck diving and not all wreck divers were happy with additional lines (ie: entanglement hazard) being layed in wrecks even on a temporary basis.

One disadvantage to using line in a wreck is that you are pretty much limited to exiting the way you entered so that the line can be removed on the way out. in contrast a diver who is very familiar with the wreck and is not using a line may plan to exit through a different opening in the wreck.

As you indicate above, wrecks are not always stable and essentially begin deteriorating the day they sink. Generally speaking lighter constructed merchant vessels deteriorate faster than more heavily constructed naval vessels.

 

[VeniVidi]

(...) Wreck lines are placed by the diver so it all depends on the skill of the diver. (...)

Exactly! And how about the skills in total silt-out? Are the skills the same you need to have when cave diving? One thing I have learned so far, is, that some wreck divers dispise the use of a wreck-line because of a high risk of entanglement. So should this be the most common style of wreck-diving, what are the bail-out procedures when one encounters no viz at all?

 

[VeniVidi]

Thanks DA Aquamaster, especially for the technical details on the lines! Now do you happen to know if also touch-contact is practised for exiting?

 

[Dive-aholic]

Exactly! And how about the skills in total silt-out? Are the skills the same you need to have when cave diving? One thing I have learned so far, is, that some wreck divers dispise the use of a wreck-line because of a high risk of entanglement. So should this be the most common style of wreck-diving, what are the bail-out procedures when one encounters no viz at all?

Silt outs shouldn't occur, but unfortunately they do, even when it's not your fault. In that situation, that line becomes my life line. IMO one additional line is worth the risk of entanglement if it's going to get you out of the overhead. The risk is decreased because you put it there and should know its route. If you're using it to exit in no viz, you should be above and to the side of it, touching it. I'm not sure this presents much of an entanglement issue, at least not one enough to forgo it. I've been silted out with absolutely no viz. Yes, I knew which way was out, but doubts were there anyway. The line eliminated those doubts.

 

[D1V3R]

Silt outs happen in caves very easily, and are sometimes inavoidable (such as passing through a restriction). In a wreck, you never ever want to cause a silt out, it is much more dangerous due to dangerous debris and entaglement hazzards.

 

[Rick Murchison]

In a wreck, you never ever want to cause a silt out, it is much more dangerous due to dangerous debris and entaglement hazzards.

True enough... you never want to cause a silt-out. But because you can, and because even the most skilled diver can't stop some silt-outs (bubbles dislodging overhead silt, for example, or, for you rebreather divers, the startled Jewfish poofing it for you), if you penetrate a wreck you must be prepared to find your way back out with zero visibility.
I use a line.
Rick

 

[VeniVidi]

I use a line.

...and with it the very same procedures like in a cave?

 

[JimC]

My worst silt out happened inside a wreck. Something about putting my arm and primary reel in a pile of silt up to my shoulder. Buddy pushed me from behind accident while in a long restriction.

You know, the whole can barely make out a white glow when you press your HID against your mask. That was fun - thank god for the line.