Considered by some to be the ultimate diving challenge, the wrecks and remains of sunken vessels hold a fascination all of their own. Leaving to one side concerns about the rights and wrongs of removing artefacts from wrecks, there’s a hypnotic attraction to the idea of gliding weightlessly through passageways, engine-spaces and compartments filled with ghosts of the past.
While most older wrecks, (particularly those in shallower waters), have collapsed and been scattered across the sea floor, others retain much of their original appearance. Some, with side and deck-plates removed – and potentially dangerous compartments permanently sealed – have been purposely sunk at the end of their working life as diving attractions offering safe and easy access to divers of every level of experience.
Many wrecks are less benign. Often the victims of structural damage they can lie at strange angles in water depths beyond the range of recreational air diving limits. With buckled plates, entanglements, collapsed decks and interiors carpeted with silt and debris, penetrating even a short distance inside their hulls is a risky business. A careless fin-kick can stir up the silt, reducing visibility to zero. Disoriented and unable to find their way out of a compartment, even the most experienced diver can succumb to panic and perish while only feet away from an exit point.
A penetration-dive into the overhead environment of a cave or wreck carries with it a greater element of risk than one with direct vertical access to the surface. The potential dangers can be magnified by depth and the attendant narcosis factors. Reducing such risks to acceptable and manageable levels begins by visualising all that can possibly go wrong during this type of dive – and then taking steps to ensure that it doesn’t!
Proper training is essential before attempting any dive into an overhead environment, especially when venturing into the previously unexplored confines of a wreck. While many Agencies offer basic courses in wreck diving it’s worth bearing in mind that it can be a complex affair. Falling outside of the scope of the normal recreational diving limits, would-be wreck divers may well need to be proficient in decompression diving procedures and the use of exotic blends of gas before turning their attention to the equipment and techniques employed in penetrating a wreck.
Apart from sea conditions, tides, currents and surge, wrecks have peculiar dangers all of their own. Because of the marine life that they attract wreck sites are popular fishing spots. Snagged and abandoned trawl nets and monofilament line create entanglements; torn metal plates may have razor sharp edges; gashes in the vessels side may prove easy entry points but – like lobster pots – be more difficult to exit from; and once inside the wreck itself the diver may have to contend with wires and cables; toxic chemicals that may have been carried in the vessel; structural weaknesses that can suddenly cause a bulkhead or deck to collapse; silt-outs that can render the most powerful light useless; disorientation; separation and loss of contact with ones companions; narcosis, and even unexpected claustrophobia.
Despite the additional equipment that’s essential to safety when diving in an overhead environment, the wreck diver should aim for a clean, uncluttered configuration that – because of the increased potential for entanglement – should be streamlined with hoses close to the body and mask and fin straps taped down.
As with all forms of technical diving, wreck diving places great emphasis on self-sufficiency. Gas management, with a suitable reserve for emergencies, is best handled with twin-cylinders. Reinforcing the importance of redundancy the wreck diver should carry a spare mask; three reliable lights, (one of which – the primary – should be a high intensity model); a line cutter – and possibly a wire cutter; a lift bag that can be readily deployed as a surface marker buoy, ascent or decompression line; two reels with heavy duty line; directional markers and arrows that, when placed along a tied off line, point towards the exit or the surface; a jonline – a short line with quick disconnect clips that can be attached to the ascent line during lengthy decompression schedules and that acts as a dampening device to reduce the up and down motion of a vessel in heavy seas; and gloves to protect the divers hands from the many razor sharp obstacles encountered on and around wrecks.
Because of the increased risk when diving in an overhead environment, the dive plan must be meticulous in its detail and incorporate a contingency plan to cover every possible situation.
Before attempting penetration divers should, ideally, make a thorough survey of the exterior hull looking for structural weaknesses, suitable access points and obstacles that may hinder an easy exit. Where doubts exist defer penetration and allow any member of the team to ‘call the dive’ for any reason and without fear of later ridicule.
One of the most basic of diving skills – and when diving inside a wreck one of the most critical – good buoyancy control is essential in avoiding sharp and projecting objects as well as unnecessary contact with deck-heads, bulkheads and other obstructions. Even finning techniques may need to be modified in order to prevent the downwash from a scissor-kick stirring up silt; the reason that many wreck (and cave) divers favour a short, shallow frog-kick.
Getting inside a wreck may be comparatively easy. Finding the way back out again can sometimes be more problematic! The two favoured methods are ‘progressive penetration’ and ‘laying line’. The former relies on gradually penetrating the hull compartment by compartment and becoming familiar with the route into and back out of the wreck: A lengthy process that’s often impractical when there’s a limited window of diving opportunity.
The second – more practical and safer – method is to carry a reel of line that, with one end attached outside of the entry point, can be spooled out behind the diver and, when reeled back in, guide them back to their exit point. It’s a technique that requires considerable practice and an appreciation of the fact that if the line is not deployed correctly it can easily become an entanglement hazard or, if the line runs across a sharp metal edge, sliced in two: A possibility that is best resolved by paying attention to one’s surroundings when entering the bowels of a vessel and the reason that most serious wreck divers use a heavier duty line on their primary reel.
When diving a wreck it’s usual to descend on a shot or anchor line. Keeping track of divers who may still be inside the wreck is made easier when each diver attaches a personal marker to the bottom of the descent line and retrieves it before their final ascent. For convenience sake, (particularly in reduced visibility), it’s often more convenient to lay a short ‘jump-line’ tied off between the anchor and the entry point, having first made certain that the anchor is firmly embedded and won’t drag.
Before entering the vessel ensure that the line is securely tied to a stationary object free from sharp surfaces and, ideally, no further than one or two metres from the entry point. Once the line is secured clip a small slate or marker to the line to indicate that divers are using the line and are still inside the wreck. (Even when the line is tied off inside the wreck for subsequent use, this marker must still be recovered prior to ascent.
On entering the wreck pay out the line, keeping it taut and away from the floor. Periodically tie off the line using a quick release cave divers knot to save time battling with a seized knot when exiting the wreck and, particularly when it’s a complicated penetration, attach directional markers to the line to indicate the exit route.
Diving in an overhead environment requires a more conservative approach to gas management than is usually the case in open water. For this reason wreck divers generally adopt the “Rule of Thirds”, consuming one-third of the gas supply during descent and penetration and reserving the remaining two-thirds for exiting the wreck and ascending back to the surface.
Encouraged by the fact that an increasing number of vessels – having first been made as safe as possible – are being purposely sunk as recreational diving attractions, many divers tend to neglect the need for advanced training in wreck-diving techniques. In doing so, they not only deny themselves the safe enjoyment of what can be one of diving’s most exhilarating experiences, but – and more importantly – choose to ignore that cardinal rule: If you’re not prepared to do it properly, then don’t do it.
The above article was first published in 1997