An open-face reel for line-laying - practise to be sure of avoiding birds-nesting

THE DANGERS OF ENTERING SHIPWRECKS ARE as real for the professionals as they are for newcomers. Incidents that occur in the overhead environment are usually the result of one or a combination of four human errors.
  These are failure to: run continuous guidelines to open water; use rule of thirds gas management (a third in, a third out, a third in reserve), use at least three light sources; and obtain proper training.
  By attending to such issues, and practising the emergency drills needed to exit a wreck safely should trouble occur, penetration can be made infinitely safer.
  As soon as you enter an area where direct access to the surface is unavailable, you have penetrated the wreck to some extent and should have laid a line to indicate your exit route. Should you want to undertake a lengthy swim inside, many prior dives may be needed, each time extending the guideline, mapping and making the intended route safer.
  Some potential dangers are obvious, others not. The wreck may be upside-down or on its side, introducing the possibility of disorientation. Passages or doorways may be horizontal, offering instant restrictions. Doorways may close behind you.
  Look behind as you swim through a wreck and you will notice the clarity of the water diminishing. As you lay line. you will dislodge silt clinging to initially clean-looking projections.
  Bubbles from your expired breath dislodge silt particles, and even if you dont touch or breathe near anything, silt rain may pour down, often triggered by your wake.
  The wreck will be unstable if it has been down for any length of time, and may have become home to many fish species, from 40kg conger eels in temperate waters to shoals of lionfish in sunnier climates. To avoid its hazardous inmates, you need a primary dive light that can last the entire dive, plus two backups.
  Metalwork could be sharp enough to cut the guideline if you pull it taut, or your regulator hoses. if you hit something above you; or exposure suits and careless fingers!

Serious wreck-penetration involves using redundant or duplicate scuba gear. Double tanks of an acceptable capacity should ideally be manifolded together with a centre isolation valve andindependent regulators.
  Hoses should exit the first stage downwards, helping to keep all valves accessible. Independent cylinders are acceptable, as are large-capacity single tanks used with dual-valve outlets, such as H or Y valves (dont use valves with burst discs!).
  The tanks are attached to each other using twin steel bands, and the set fastened to a wing-style BC using wing-nuts or similar. They should be free from obtrusions.
  Some divers remove tank boots to give a cleaner profile so that line and ropes can slide off more easily.
  The left-hand first stage carries the systems pressure gauge, inflator hose for the wing and the short-hose secondary regulator, which is kept close to the divers mouth by bungee cord or surgical tubing. The right-hand regulator carries a long-hose primary regulator, which can be up to 2m long and looped around the divers neck or tucked along the tank under the bungee.
  The long hose should be breathed off at all times unless handed to an out-of-air partner, when the donor switches to his short-hose regulator.

You need one large penetration reel (say 100m of line) per buddy team, and smaller safety reels with 30-50m lines for each diver. There are many types of penetration reel but choose a good one of stainless steel, preferably with a simple friction knob.
  Too often a diver deep inside a wreck has seen his cheap alternative reel fall apart, leaving a reel body wrapped in bundles of line.
  Keep the friction knob or locking plug all the way out to ensure free-running. Add some friction by using your forefinger as the line pays out.
  Enclosed reels minimise line overspilling the edges, but once jammed they cannot be fixed easily, if at all, under water. Open-face reels need closer attention to avoid overspill line jams, but practice and patience can avert a birds-nest scenario.
ÂÂÂÂ Smaller safety reels are used if you lose sight of the guideline. Tie off the reel and use it to search for the main line. Clip it to the main line at this point to be recovered later.
  Bare spools are simple and popular but again take practice to avoid birds-nests.

A primary light should have a lantern handle or a wrist-mount (sometimes called a Goodman handle), so that you can hold it in the same hand as the reel, leaving the other free.
  A narrow beam spread will avoid the light-scatter problems associated with poor visibility.
  Primary lights are often very powerful and require large batteries. Battery packs for large dive lights are usuallyrechargeable, preferably non-acid because of their lower maintenance schedules but be aware that they tend to exhaust without warning and are far more expensive than the lead-acid type.
  Lead-acid rechargeables have a memory effect, and require regular charge/discharge routines to maintain performance. High Intensity Discharge (HID) lights are becoming more popular, as they offer superior brightness and burntimes from smaller battery packs.
  The downside is a lack of robustness and sometimes-prohibitive cost of replacement bulbs and ballast packs.
  Carry at least two small back-up lights powered by fresh disposable batteries. The lights should have small piston-clips attached and be worn in the chest area of the wing harness for easy access.
  As you descend, most twist-on type lights will turn on as the pressure squeezes their bodies.
  Inspect your back-up lights often on the dive and let your buddy know if his are on. Avoid putting put back-up lights inside pockets.
  Head-mounted or helmet lights can be effective in certain conditions because they leave your hands free, but dont let them become entanglement points, or blind your buddy every time you look him in the eye.

wings and harnesses
Your BC must have ample buoyancy to counteract your heavy tanks and the inevitable loss of buoyancy from your suit as depth increases.
  Wrecks are sharp places, and many divers have punctured drysuits or BCs in tight spaces, so redundant buoyancy is necessary.
  This can take the form of a single air-cell BC and drysuit or, for the wet-suited diver, a dual-bladder wing. Many advanced divers adopt a harness and backplate system with a wing-style bladder. This set-up takes the weight of the dual tanks easily, leaving the back wing to inflate freely.
  Debate about bungeed or non-bungeed wings can get heated but either, when used properly, offers a safe system.
  The bulking caused by bungeeing may add a little drag, but thecushioning against sharp edges gives some extra puncture protection.
  Bungeed wings offer a more balanced trim, the bungees being necessary if the wings are bigger than, say, 25kg. Adding strips of car inner tube to the inner wing bag can help here, too.

things that might snag
If using manifolded tanks, you will have only one pressure gauge, which can be attached left or right as required. It should have a piston clip attached with a small cable-tie or nylon string to act as a breakaway should line get tangled around it.
  Depth gauges or compasses should be wrist-mounted. Knives should be worn on the upper body, ideally on the wing-harness waistband or lower arm for easy access.
  Carry at least two sharp cutting devices and inspect them regularly. Coat the cutting blade often with silicone grease to prevent rusting. The more you spend on a dive knife, the quicker it will rust!
  On fins, cover any possible snag points with gaffer tape. Fin-straps can be reversed to make them smoother.
  Large free-diving fins should not be used inside wrecks. A recent trend in using springs for fin straps shows the power of marketing but they really are a line magnet !
  A backup mask comes in very handy should you lose yours. It should be low-volume enough to fit into your suit pocket (if you have none, you can buy the self-stick variety).
  Few wing and harness systems come with pockets; you have to order them separately.
ÂÂÂÂ Carry only small life-support spares in pockets, such as spare mask, spare back-up reel, backup decompression tables, trauma shears and so on. Dont stuff too much in.

gas requirements
Remember that without benefit of the assisting currents which you sometimes find in caves, the time needed to exit a wreck will be the same or longer than the entry time. You therefore need to plan your dives conservatively.
  With all decompression dives you will have a turnround pressure based on the rule of thirds.
  If the planned decompression time is in excess of 10 minutes, deco gas reserves should be factored into the dive plan.
  Calculate your personal RMV (Respiratory Minute Volume) to help you work out tank sizes and fill-pressures for future dives.
 To find it, swim at constant depth (say 20m) for a fixed time (say 10 minutes), noting starting and ending tank pressures.
  If you used 45 bar, divide by time (10 minutes) and then by atmospheric pressure at the depth (3 bar). The answer is 1.5.
  Now multiply this figure by your tank size in litres. If you used a 15 litre tank, multiply 1.5 x 15 to get a 22.5 litres a minute gas consumption rate.
ÂÂÂÂ It will now be easier to calculate your requirements according to the rule of thirds, always leaving a third in reserve once you exit the wreck.

You will encounter various types of silt in a wreck. Sand grains generally fall out of suspension quickly but mud is more serious. Its easy to disturb and may take a long time to settle.
  Clay is even worse, readily disturbed, taking hours to settle and sticking to anything.
  Some parts of the world are prone to volcanic ash, which poses a serious problem because of the usually large volume of deposit and the fineness of the particulate.
  Finally, many forms of silt derive from the wreck itself, including rust particles, carpet fibres, coal dust, hardboard, wood and expanded foam panels, and oil/fuel residues.
  As floors become ceilings and sidewalls floors, the basic approach is to touch nothing. Watch where youre going and use the most appropriate propulsion techniques.
  In areas of suspected silt build-up, stay closer to the guideline, towards the top of a passageway and a couple of feet from the sides.

If space allows, use the shuffle-kick (a modified flutter-kick) or a frog-kick, but if passageways are narrow or you are passing through a hatchway, use the pull-and-glide technique.
  These methods send all propulsion force behind you instead of downwards or sideways, and should be mastered in a pool before being practised in a wreck.
  A shuffle-kick involves flexing the legs below the knee only. Keep the thighs in line with the body and knees bent at 90Â, and move the fins back and forth down to the midline and back. Fin-wash should be directly backwards.
  A frog-kick is trickier. It involves kicking with both fins at the same time, the fin-wash being directed inwards and backwards. Once mastered very little effort is needed, but you do need perfect buoyancy control.
  Pull-and-glide means using fingertips (avoiding sharp edges) to propel yourself gently forwards. Watch the position of your legs and fins to avoid contact with the wreck.
  Pull-and-glide is also a good way to avoid exertion when current speeds are high and movement outside the wreck is needed. With all three techniques, keep head low and feet high.

In the overhead environment you will need to memorise new dive-light signals, learn some squeeze signals to use in poor visibility and combine these with an emergency procedure called the Rimbach System.
  The light signals are done with the beam shining below your buddys line of sight, so as not to ruin his night vision.
  The lead diver asks OK, by projecting a circular OK on the floor or wall. An attentive buddy should see this and return the signal just in front of the first signal.
  A side-to-side movement of the light indicates attention, while a wider arc means problem.
  Other signals to learn include reel line (a circular motion); line entanglement (a figure eight); stuck! or hold (stop); deco status (a loose OK movement around the line); and up or exit (back-up light on).
  The signals for OK, hold and exit are control signals; return them so that the signaller knows they are understood.
  Covering your light beam and searching for the glow of a partners light can sometimes find a lost buddy.
  Dont turn your light on or off more than is necessary, to avoid stressing bulb filament, especially with High Intensity Discharge (HID) lights.
  The Rimbach System was devised by cave-diver Don Rimbach to allow several divers to exit the overhead environment as a group when visibility is bad.
  When visibility is compromised, the lead diver waits on the line for the one behind to touch him above the knee, where the second diver pushes once to say go, or squeezes once to say stop exit or wait.
  To back up, the second diver pulls back on the leaders leg.
  When all are assembled, the last diver pushes the next one and so on, and the group exits maintaining a loose OK on the line until visibility improves.
  In the event of an entanglement, the diver squeezes the one next to him to signal stop.
  Should a diver need to back up, he simply pulls back with his hand and the group waits until the problem is fixed, then pushes to go on. Team-members should maintain contact at all times when visibility is compromised. Practise.

Never put more than your head into any holes in a wreck without first tying off your reel. This primary tie-off must be done in open water.
  As you swim inside, look all around to see how the passage unfolds.
  Look for a secondary tie-off, to ensure that, if the primary is tampered with outside, you still have tension on the guideline.
  You should be able to see open water from the secondary tie-off position.
  Good line technique is an art. Pay the line out while swimming slowly, the reel held below you and to one side.
  Look for areas to place the line to keep it from straying into the middle of the passageway, or into any potential line traps, areas where the passageway narrows to such an extent that following the line with a loose OK would be difficult.
  The line should be 7-10cm from the wall and as close to the middle as possible. Avoid laying it close to the ceiling, as it may end up above you and cause entanglement.
  Try to visualise having to follow it back out in zero visibility, perhaps even air-sharing. Keep some tension in the line, but not so much that it might get cut against a sharp edge.
  Line-wraps are a way of securing line by passing the reel body around a potential fixing. As they cannot be removed for you, and are more difficult to follow in limited visibility, they should be avoided.
  As you progress through the wreck, your buddy may redo certain line-placements or add some extra tension. As you make placements, a good buddy will shine his light to help you, and as you exit, he should remove line placements, help with any line wraps and keep the guideline taut.
  Remember that if you cross the line at any point, do so above it. The first diver in is the last out - dont switch positions.

stress management
As with all new environments you may feel uneasy at first, or even later on. This is normal. But while a small amount of stress keeps you focused; too much can lead to problems.
  Accident analysis has revealed that stress could be the leading cause of death in diving, and recognising and controlling it is another skill that needs honing.
  Practice and repetition removes the stress caused by lack of experience. If you became over-exerted while exploring deep into a wreck, would you recognise the subtle changes that your brain engineers to warn you to re-evaluate the dive
  Ask: Am I cold Am I too deep Why is the anchor stuck so fast in the wreckage
  Do you recognise these stressors A poor nights sleep, bad weather, alcohol consumption the previous night, seasickness, a long car ride, strong current, a long boat journey, poor visibility, stomach complaints, lost equipment, inexperience, equipment failure, peer pressure, narcosis - its a wonder we even bother sometimes!
  Any of these can mark the start of an underwater problem. Symptoms of stress include yawning, fatigue, depression, lethargy, doom radio in the head, unco-ordination, clumsiness, lack of concentration, perceptual narrowing, task-fixation, shivering, overexertion or panic.
  A combination of these symptoms could overload you and affect your performance. Initial anxiety and loss of self-control may lead to panic and such problems as rapid gas consumption or entanglement.
  To avoid it requires self-honesty, continual skills practice, equipment familiarity and willingness to stay within personal limits.
  If you feel bad, dont dive. If already under water, ascend before you enter the wreck. Make up an equipment-related problem if you wish, but surface early. And if youre in the wreck, get out as soon as possible.

safety first
Should you become separated from your buddy inside the wreck, exit and wait by the entry point to be reunited. In poor visibility a line should be laid from the dive boat anchor/shotline to the entry point. Dont search alone for a buddy who may already have exited the wreck.
  I started with the four common failings in wreck-penetration dives, but there are also four golden rules. These are:

  • Dont remove your equipment;
  • Dont enter any restrictions or rooms too small for two divers to enter together;
  • Observe the rule of thirds;
  • Keep within maximum depth limits according to your level of training/experience.
do a course
Wreck-penetration techniques are beyond the limits of standard wreck speciality courses, which are aimed at the fairly new divers seeking more interesting dive destinations without the hazards of entering an overhead environment. If youre serious about safe wreck-penetration, obtain advanced wreck-diver training.
  Finally, accept expert advice on what is and is not safe on a wreck - and dont even think about penetrating war graves or wrecks on which penetration is prohibited on safety grounds.

Torchbeams are used for signalling by projecting onto a floor or wall - this means
Standard fin-kicking with straight legs is guaranteed to disturb silt deposits...
One solution is the flutter kick, with knees bent at 90¡ to keep the fins away from the floor
Another way to avoid disturbing sediment is the frog kick
No activity should be carried out inside a wreck unless the diver is well-prepared