Kategorie: News
The answer depends very much on what you mean by ‘diving’…
Editor’s note: This article is aimed at divers and non-divers alike. We hope it helps non-divers to better understand the sometimes confusing media coverage of diving-related topics, and we’d be delighted if you shared this article with your non-diving friends.
Article by Tim Blömeke, first published in DAN Alert Diver
On 14 May, a group of five Italian divers swam into a sea cave in the Maldives known as Devana Kandu. None of them returned to the surface. The local authorities and the diving insurance organisation Divers Alert Network Europe (DAN EU) organised a recovery mission led by the Finnish cave diver Sami Paakarinen. The team arrived in the Maldives on 18 May. Three days later, all five bodies had been recovered from the cave and brought to the surface.
Unfortunately, the process of obtaining the necessary permits and the team’s journey did not take place in time to prevent the death of Mohamed Madhudhee. Madhudhee was a military diver and non-commissioned officer in the Maldivian Armed Forces. He died as a result of a severe decompression accident during a recovery attempt on 16 May.
Much like the incident in Thailand in 2018, the story made headlines worldwide and was discussed in numerous leading media outlets, including The New York Times.
Diving and the attention economy
Most of the time, diving takes place away from the public eye. Divers talk about it constantly, whilst non-divers hardly ever give it a thought. This changes briefly when something goes wrong in a sensational way, until the news cycle moves on and the diving stories disappear into the archives.
Unlike the stock markets and the entertainment industry, there are no journalists in the mainstream media who specialise in diving. Reporters who are suddenly tasked with covering a diving accident inevitably lack the contacts to relevant sources who could assess a case with expertise.
No one is really to blame for this, least of all the journalists themselves: we all work to earn a living, and as a writer specialising in diving, I can attest that my choice of subject matter is not necessarily conducive to a high-flying media career.
Unfortunately, however, the situation described above means that the non-diving public is presented with a distorted picture of the sport of diving. Media coverage tends to focus on extraordinary accidents. Hazards such as caves and sharks, which attract a great deal of attention, are not representative of the considerably less dramatic risks that ordinary divers have to learn to cope with.
Recreational diving
The aim of recreational diving is enjoyment: experiencing weightlessness underwater, exploring marine habitats, and perhaps taking photographs or videos of fish, turtles and the myriad fascinating species of marine micro-organisms.
The vast majority of recreational diving training takes place in accordance with the rules of the World Recreational Scuba Training Council (WRSTC).
The WRSTC has set a depth limit of 40 metres. The breathing gas supply is (usually) a single cylinder of air or nitrox. Nitrox is air with a slightly higher oxygen content.
The time spent at depth (bottom time) must be calculated so that even a relatively rapid ascent would entail only a minimal risk of decompression sickness. Diving in confined spaces where there are barriers to a direct route to the surface (wrecks and caves) is permitted only to a very limited extent: divers must remain within daylight range at all times, and the total distance to the surface (the sum of the dive depth and the horizontal distance travelled) must not exceed 40 metres.
These are the rules under which the vast majority of dives worldwide take place. The basic principle is to limit dives in such a way that an emergency ascent to the surface is possible at any time without unreasonable risk. And it works really well.
Safety and Level of Difficulty
Like other outdoor activities, diving is not overly regulated in most countries. Official accident statistics are scarce. However, there are organisations that deal with diving safety on a daily basis: specialist accident insurers such as the Divers’ Alert Network (DAN).
Diving accident insurance (excluding travel insurance) is available for around 100 US dollars and covers medical treatment costs. The low price is a clear indication that diving – in the opinion of those who deal with the matter professionally – has a very good safety record.
As far as difficulty is concerned, recreational diving is about as demanding as driving a car. Yes, it requires a little training and practice, but virtually anyone can learn it and practise it with a high level of safety – provided, of course, that you stick to the traffic rules and speed limits.
When divers venture into areas outside the scope of the WRSTC rules, things very quickly become quite complicated – for reasons that are not necessarily immediately apparent. In the following sections, I shall attempt to explain these complications in as simple and accessible a way as possible.
Diving in enclosed spaces
Enclosed spaces (shipwrecks and caves) prevent a direct ascent to the surface. Before this becomes possible again, divers must first make their way back to the exit. When planning dives to wrecks and cave systems, a horizontal distance must therefore be taken into account in addition to the vertical ascent. Covering this distance takes time, and time means breathing gas.
The interiors of wrecks and caves can be veritable labyrinths and are often pitch-black, with no light whatsoever. Cave divers therefore mark their route to the exit with lines – Ariadne’s thread – and carry several torches for redundancy. Because delays can occur, time spent underwater means consumption of breathing gas, and no piece of equipment is immune to failure, carrying additional cylinders (at least two per diver) is an absolute must.
Deep diving
Depth brings its own complications. For every ten metres, the ambient pressure increases by one atmosphere. This pressure, in turn, increases the density of the breathing gas, which has a whole range of consequences.
A diver at 50 metres inhales six times the volume of air into their lungs with every breath compared to at the surface. On deep dives, breathing gas is therefore consumed considerably faster than in (relatively speaking) shallow water.
Secondly, the ambient pressure causes gas to dissolve into the bloodstream and be carried via the circulatory system to all the body’s tissues – the deeper the diver goes, the more gas dissolves and the faster this process occurs. When the ambient pressure decreases again during ascent, the gas is released from solution and must go somewhere.
If the pressure drops too quickly due to a rapid ascent, the gas forms bubbles within the diver’s body. These can cause a wide range of symptoms, collectively known as decompression sickness (DCS). In mild cases, the symptoms are limited to an itchy rash. Severe cases can involve paralysis and stroke-like symptoms, and may even be fatal.
For successful decompression, divers must ascend slowly enough for the gas to pass in a controlled manner through the bloodstream into the lungs, where it can be exhaled. The ascent from a deep dive can take several times the duration of the dive itself, and divers must carry a sufficient supply of breathing gas with them.
Thirdly, both nitrogen and oxygen – the two main components of air and nitrox – cause problems under high pressure. They have a narcotic effect and impair mental and physical performance. The sheer physical density of the gas makes breathing difficult. Furthermore, under high pressure, oxygen has a toxic effect on the central nervous system.
To counteract these effects, technical divers use gas mixtures containing helium. Helium has a very low density and does not have a narcotic effect. The disadvantage is that helium mixtures with a low oxygen content are far from ideal for decompression in shallow water. For this, additional cylinders containing other mixtures are required; these, with their higher oxygen content, are optimised for the final phase of the dive in shallow water.
A different calibre
Most people will probably have noticed by now that the term ‘additional cylinders’ keeps cropping up. Diving cylinders are bulky and heavy, and they must be secured to the diver’s body in such a way that they do not hinder the diver too much underwater. Cylinders have breathing hoses. These must be easily accessible when needed and safely stowed away when not in use. Procedures to ensure that no one breathes the wrong gas at the wrong depth are vital.
Well-trained divers are increasingly using closed-circuit rebreathers (CCR). These devices recirculate exhaled gas, chemically remove carbon dioxide and replenish the oxygen consumed by the body. The use of rebreathers makes a dive considerably more complex and requires its own, separate training. The advantage is that these devices drastically reduce gas consumption, allowing divers to remain underwater for much longer.
These complications do not make deep and cave diving inherently dangerous. However, these types of diving require specialised equipment and comprehensive training in its use.
Most divers, even diving instructors and other professionals, have no need for this training. It is therefore not part of the standard curriculum for recreational diving.
Experience in recreational diving can be helpful in technical diving, but it is by no means sufficient. To return to the comparison with driving: 30 years’ experience as a taxi driver does not qualify anyone to reverse a articulated lorry into a parking space. The attempt would almost certainly fail.
Safety
With the appropriate training, equipment and preparation, deep and cave diving are not particularly risky. This is reflected in the fact that insurance companies do not charge higher premiums for these types of diving.
Good divers, whatever their level, are explorers, but not risk-seekers. On the contrary: we do our best to make dives as predictable as possible.
Adrenaline and the fight-or-flight response are less than useless underwater. We practise replacing our instinctive reactions with learnt skills and procedures. Unexpected incidents are discussed during the post-dive debrief. Every instance of ‘that was a close call’ would be cause for thorough self-criticism.
From decompression procedures to laying lines, calculating breathing gas reserves and bailout procedures in rebreather diving: Our current understanding of diving safety is largely based on the hard lessons of the past… Learning from these, adhering to standards and keeping up to date with the latest scientific knowledge is a form of respect for those who have paid the price for this knowledge.
The Author
Tim Blömeke is a TDI Instructor Trainer and teaches technical and rebreather diving (Fathom MkV mCCR) in the Philippines and Taiwan. He is the editor-in-chief of Alert Diver, as well as a freelance writer and translator. For course enquiries, article suggestions, comments, etc., he can be contacted via his blog and on Instagram.
More information:
DAN Alert Diver
This article was first published in DAN Alert Diver