Tuesday, March 25, 2008

Cave Skills Part 1 : Why Use a Line ?

Thanks to pioneers like Sheck Exley cave diving is not as risky as it once was. His survey of caving deaths and the subsequent principles that every cave diver should follow was instrumental in eliminating the inherent risk of being underwater in a cave. Interestingly, the first contributing cause he identified was NOT using a continuous guideline (see the blog post, Blue Print for Survival). These days not using a guideline is the exception rather than the norm, but back in the early 90’s using your memory was an accepted alternative. Indeed there was a continuous argument between divers who preferred to ‘learn’ the system (memorise the way in and out) and those who relied on lines to get them in and out. With each claiming the others method to be dangerous.
Those who argued for memory maintained that if you lost the line you had no way of using visual queues to get yourself back onto it (and so out) as you never had to ‘learn’ the system. They also argued that using a line emboldened divers who then went further than they should which got them into trouble. When you dived using your memory (they argued) penetrations were slower requiring a number of dives in order to create the memory imprint of the route. This meant that risk was added slowly and so the chances were that should something go wrong, the diver would get out. The problem with this philosophy is that overhead environments are notoriously easy to silt out (not to mention the fact that light sources can fail). This meant that exiting the cave could often occur in the dark, which in turn meant that ‘learning’ the system only worked if you also learnt it in the Braille version.
No matter which way you look at it, the only reliable way of returning from a silt out (or any other emergency) is using a continuous guideline ? What that means is that you must be able to find your way back to the surface using either the line you laid or a line that is already in place. This line must at all times connect you to the safety of the surface, without any breaks or jumps. In an emergency all you should need to do is follow that line and most importantly, you should not require any light to do so (and preferably little effort and thought).
Practically this means tying off just before you enter the cave system (preferably where inquisitive sport divers can’t find the line and tamper with it or even worse, follow it into the cave). As the guideline is your life, you have a secondary tie off just inside the cave system or entrance which ensures that the line will always be there (just in case an inquisitive sport diver removes your primary tie off outside).
If you are lucky you will be the only dive team diving the cave system however more often than not, yours will not be the only line wending its way through the inky darknesss. In this instance there are two choices open to you. The first is to piggy back on the lines that have already been laid. This will require you locating the owners of that line and negotiating with them to use their lines. Some divers are happy with that, some not. And don’t be tempted to avoid the asking and simply use the lines. Divers can get quite territorial about their lines, not to mention the fact that you stand a real risk of the line being removed while you are still diving (can you imagine getting to a tie off and finding that the line you came in on is no longer there ?).
Quite a few divers avoid sharing and instead lay their own line. If there are other lines already in place then basic line laying etiquette dictates that you always lay your line under existing lines. The argument goes that should a team already be in the cave and need to exit in an emergency they will not know about your line as it was not there when they went in. Should they encounter a new line over theirs it could cause confusion and delays. If the line is under theirs they can ignore it and get out quickly and safely.
One other advantage of laying one’s own line is that you control the location and frequency of the tie-offs. The number and location of tie-off’s is one of the most frequently asked questions by new (and old) cavers. Divers tend to fall into two categories, either too many or too few tie offs. Nerves tend to increase the number of tie offs, while confidence tends to reduce the number. Both extremes are problematic. The line is there to get you out as fast as possible in an emergency where you have no visibility. Tie-off’s are obstacles which have to be negotiated. If the diver was meticulous the obstacle around which the line was tied off (normally a convenient boulder) is ‘invisible’ and the line flows in a single unbroken line straight past the boulder. However if this is not the case each obstacle has to be negotiated by touch in order to find the ‘exit’ point of the line. Not what you want in the dark.
The other problem that divers encounter when exiting a line is that of unforeseen obstacles or line traps. The rule of thumb is to tie off when you change direction. This will prevent the line from swinging into the wall and boulders or narrow crevices. This is easier said then done as direction changes can be subtle and often the only time you realise the line has moved is when you swim back on it and find it has tucked itself neatly into a crack. That is when you thank the heavens that you are not exiting in an emergency and make a mental note to add a tie off next time round. The trick is to keep looking back - that way you can see exactly how your line actually is lying and add a tie off it needed.
The next question normally asked is how many tie off’s is enough. There is no simple answer as that. A well laid line enables the diver to exit fast, in the dark. It also ensures that the line is always in an area a diver can pas through. A well laid line is also taut. Too few tie off’s can create a loose line as can badly tied tie off’s that come loose during the dive. Loose line can move…normally toward those cracks and crevices. It also is an entrapment hazard.
How do you know if your line is well laid ? The easiest answer is to ‘practice’ leaving on the line while pretending that you are doing so in the dark - that way you will see for yourself. Whether or not you are in the habit of ‘practicing’ on the way out, you should at least one official and real practice from your cave course. Even with a couple of practiced silt outs under my belt (and a handful of real one’s) I still find them stressful. My heart rate increases and with that comes a nagging doubt that this time something will go wrong. Do I have enough gas ? Will the line hold ? There is one place in particular that I do not enjoy, the restriction on 7th level (going to the old station) at Badgat. This is fine on the way in (a little tight but no problem if you are number one or two). But when you come back out it can be a complete silt out. Now I know that the line is well laid and that if I follow it I will be in the widest part of the restriction so there is no problem… but there is always that niggle, especially as you casually swim after what is after all a rather frail line that disappears into clouds of swirling silt. What if I take my hand off for some reason ? What if I do not find it again ? It is not simply a matter of placing your hand where you think you left the line. In a silt out you can never tell which direction you are in fact facing. It is easy to turn around without realizing it and at 80 odd meters gas is not something you take for granted (even with full conservative gas planning).
The panic never takes hold. I have been diving in caves for too long for that. But it is always there, a reminder not to get too confident. A reminder that the basics are essential if you want to survive and explore.