Life lines

While the element of danger can never be removed entirely from diving in an enclosed environment, a well laid line can greatly reduce the risk of a mishap for the cave or wreck diver.
By Gavin Newman.

As a cave diver I'm often told by open water divers that I must be mad to dive in caves, but in many respects entering a wreck can be even more dangerous.
Caves are natural features and, by their very nature, inherently stable. Wrecks are man-made and not generally designed to last under water. Time and the elements soon take their toll on a wreck's structure, rapidly weakening it.
After a while, a situation can often develop where it is only the density of the water surrounding it which supports the remaining structure. Replace that water with pockets of air (your exhaust bubbles ) and that support is suddenly altered.
In an extreme case this can result in the collapse of the whole structure, although the more usual short-term result is the collapse of small particles into the water, rapidly reducing visibility.
A common misconception for overhead environments is that, so long as you stay off the floor, you won't destroy visibility. In practice, ceilings and walls also attract deposits of silt and algae - and, in the case of wrecks, rust particles. All are easily dislodged by a passing diver's bubbles.
Because the diver is passing, the situation is doubly dangerous as he is often unaware of what is happening behind him. Swimming into a wreck, he is always moving into relatively clear water. It is not until he turns round to exit that he encounters silt stirred up on the way in.
By then it is too late to do anything about it. Visibility can rapidly reduce to a few centimetres, blotting out all light. Finding the way out becomes a matter of luck.
While not totally eliminating the dangers, a well laid line and an awareness of the threat to visibility from above can greatly reduce risk to the cave or wreck diver.
Line reels come in a wide range of shapes and sizes, designed for many different applications. For short wreck penetrations, probably the most obvious starting point for an open water diver is an SMB reel. These will usually hold about 40-50m of line and most divers already own one. This, unfortunately, is about their only advantage. Most SMB reels have a ratchet system to lock the reel unless a finger catch is released. While ideal for towing an SMB, this can be very awkward when trying to lay line smoothly.
For this use, you're far better off removing the catch system from your SMB reel or, ideally, buying a purpose-built exploration reel.
Such reels come in a variety of designs and sizes, usually in a combination of plastic and aluminium. Aside from differing capacities, two main designs exist: open or enclosed.
Open reels are generally cheaper and lighter, but the line can sometimes spill off the sides, causing the reel to jam. Enclosed reels generally avoid this problem, but if you do get a jam, they can be much harder to sort out under water. In the end it comes down to personal choice.
Small safety reels are designed for jumping gaps between permanently laid lines, or as personal search reels. They usually carry about 15m of line. If you are undertaking any sort of penetration diving, you should consider such a reel as essential safety equipment, regardless of whether you are following a pre-laid line or are laying your own line.
The standard or primary reel is used for laying the main exploration line. Holding anything up to 120m of line, a primary reel is usually carried only by the lead diver.
Various larger exploration reels are available. If you build your own the sky's the limit, but very large reels generally have applications only in major cave explorations.
If, though, you do want to make your own reel, be sure of your engineering skills. A reel that falls apart will leave a lethal net of loose line between you and the exit. Also, you would need to resist loading too much line on to the reel, particularly on an open spool.

In an overhead environment, your dive line can be both your best friend and your greatest enemy. Not laying a line is undoubtedly the greatest cause of cave diving accidents, with badly laid lines running a close second. Just trailing a line behind you is not enough.
You must lay a line correctly or you could be laying a death trap for yourself and anyone following.
The two most basic rules are to keep the line taut and to think where it's going to end up when you pull it tight at the next belay.
Laying a line down a passageway and round a few corners in good visibility can be really simple. Trying to follow it back out again when you can only feel the line and not see it can be a different story.
Good belaying and an awareness of where the line may pull into constricted sections difficult to negotiate on your return are, then, the key factors in safe exploration.
Wrecks usually provide a wealth of good belay points, but these should always be checked for integrity and any sharp edges. Even a heavy-gauge line can easily be cut by a rusting metal edge, so you need to be aware of anything which may cut the line if it gets pulled hard by accident.
At the start of your penetration, the line should be belayed outside the wreck in open water, then re-belayed just inside but well in sight of daylight. To double-belay like this may seem excessive, but some divers have a strange tendency to untie apparently unattended bits of string.
Getting into the habit of using double-belays might save your life one day. For maximum safety a dive slate, stating clearly that the line is in use and should be left well alone, can be attached to the outside belay.
Once inside, ideally you should lay your line in straight runs, belay to belay, and always try to avoid zig-zagging down passageways. A line which keeps jumping about means that you will probably have to keep crossing it, which puts you at maximum danger of getting snagged by it. You will also have to change hands if physically following it.
Changing hands may not seem a dangerous thing to do, but that depends on how you are following the line. If the line in your hand is under any tension, then as soon as you let it go it can easily 'ping' off into the gloom and, unless the viz is good, you can easily lose it.
If you are physically following a line, you should do so using only your finger and thumb ringing the line in an OK signal. This will stop you pulling yourself along the line, but you still need to be aware of any sideways tension you're applying. So what do you do if you accidentally lose the line? First, don't panic. At this stage it is probably only an arm's reach away. The most important thing is that you don't lose your orientation, so immediately grab hold of something close by or settle to the floor.
If the visibility is good enough, do a visual search with your light, remembering that, if you hold the lamp as far away from your eyes as possible, you get less back-scatter and better apparent visibility.
Think carefully about how the line was laid on your way in. Which side of the passage was it on? It's now that you'll appreciate having laid your line well.
If you're in a large or complicated space and you still can't find your guideline, you need to make a search using your safety reel. Tie your line off to a suitable belay on the passage floor and, assuming you have not lost your orientation, turn at 90 degrees to the direction in which you think the main line runs.
Then, laying your safety line behind you but not belaying it as you move, do a detailed search in a loop along the floor, up the wall, across the roof, down the other wall and back to your safety line belay.
If your main line has pulled against the floor or walls anywhere, you should find it en route. If it is free-floating in mid-passage, then by pulling in your looped safety line you should ensnare it. Losing the line in the first place can be scary enough, but finding it again and then not knowing which way to swim to safety can be just as bad. In cave diving, lines are tagged with both distance and direction markers, particularly at any junctions. Various systems are adopted, from simple knots in the line, through adhesive tape markers, to specially designed plastic arrows which fix to a pre-laid line.

While loosely laid line can be nearly as dangerous as no line at all, even well laid line can catch you out.
Check your kit for things that might catch on the line. Secure all your gauges and hoses so that they don't hang down, and tape up any loose fin straps and buckles. Fin straps are the most common snagging point and, next to back-mounted tanks and valves, can cause the hardest foul-ups to escape from.
Only as an absolute last resort should you cut the line to escape. After making sure you have a firm grip on the outward line, you should cut it as close to your body as possible. Reaching a leg-mounted knife can be difficult if you're in a confined space or have just trussed yourself up like a chicken, so think about wearing an arm-mounted blade.
Most line entanglements are easily escaped from, but thrashing around trying to fight the line can make things ten times worse, quickly destroying any viz you may have had.
As soon as you realise you have a problem, stay as still as possible and try to work out what has happened. Usually a simple movement in the right direction will free you. If your buddy is close to hand, stay still and let him sort it out.
If all this has seemed over the top for a simple wreck penetration, remember that few cave divers would ever stray far from the safety of their guideline, let alone dive without one.
The same should hold true for the wreck diver, whose environment can be the more treacherous of the two.
Laying and following lines may appear an easy matter, but good line-laying is an art, and one day it could save your life.