Tragic accident at Maldives: five Italians lost their lives during a dive at over 50 meters deepin the underwater caves ofVaavu Atoll. The episode was defined by local authorities as one of worst diving accidents in the history of the Maldives (made up of 1,192 small coral islands distributed over approximately 800 km in the Indian Ocean). Meanwhile, victim recovery operations have officially begun after a series of delays caused by adverse weather conditions. The specialized personnel of the Maldivian Coast Guard reached the area, accompanied by a expert Italian diverwhich is collaborating with the authorities in the most delicate phases of the intervention.
The causes of the accident have not yet been clarified, but in the last few hours there has been talk of the possibility that the group remained trapped in a cave about 60 meters deep, as well as the hypothesis that they encountered one sudden current that would push them down. To better understand how diving at depths of over 50 meters works and the possible causes of the accident, we interviewed Dr. Pasquale Longobardi, Medical director of the Hyperbaric Center of Ravenna and Vice President of the Italian Society of Underwater and Hyperbaric Medicine (SIMSI).
We are talking about dives beyond 50 metres, technical dives and recreational dives, what is the difference?
We talk about technical diving when you do a change of respiratory mixturemeaning technically you change the tank and breathe a different gas during the dive. If we imagine the diver with the tanks on his shoulders it is not a question of technical diving but of recreational diving (or tourist, as we call it). If, however, I carry one or more tanks on my side (sometimes even three) and change the mixture during the ascent, then that is technical diving.
In the case of the accident in the Maldives we could define it an open circuit divebecause it did not fall within the scope of recreational-tourist diving, but nowhere does it appear that they had accessory tanks with different mixtures. According to the information we have available, the group was in the Maldives to carry out some scientific divingpart of a project authorized by the local government, but this specific dive was not part of the scientific program.
How do you plan a dive to 50 meters depth?
To plan a dive, including those deeper than 50 meters, arisk analysisstarting from the top. The first aspect to evaluate is suitability and training of those who dive: in this case, of five people, at least two had recently undergone suitability tests. The other two were instructors who lived in the Maldives, therefore aware, and a girl in her early twenties. In short, from a health point of view they shouldn’t have had any problems.
On the training front, Professor Montefalcone had received the Golden Tridenta recognition from the International Academy of Underwater Sciences and Techniques given to the best in the world in the marine field. Having that award means being extremely competent, and the other members of the group also had experience and skills.
Once these conditions have been verified, we move on to the actual planning: we decide when and where to dive, with which mixture and with which equipment.
What breathing mixture should be used for these dives?
To understand this point we must start from a fundamental concept: our body does not “read” the depth, but the density of the gas that we are breathing. The human tolerance limit for gas density is 4 grams per liter: once this value is exceeded, the body triggers an inflammatory response.
That said, if you want to go down to 50-60 meters deep, you usually use a mixture composed of nitrogen, oxygen and helium. Helium, in fact, is fundamental because it has a very low density (0.5 g/l) and serves to lighten the total mixture. However, helium is almost never used in the Maldives because it is very expensive and difficult to transport.
Alternatively, therefore, air is useddespite knowing that at 50 meters we are right at the operational limit since at those depths it reaches a dangerous density of approx 9 grams per literexposing the body to inflammatory stress.
And what about Nitrox?
What they definitely couldn’t have used is the Nitroxwhich is air enriched in oxygen: normally air contains 21% oxygen and 79% nitrogen. With Nitrox I can increase the oxygen (to 30% or 40%) and consequently reduce the nitrogen, which is responsible for the so-called “decompression accident”.
However, if you raise the oxygen too much you risk la oxygen toxicity: an excess of this element increases electrical activity in cells with the risk of convulsions.
The causes of the accident are not yet known: are there any hypotheses that you would exclude, considering that it involved an expert group?
Among the three most frequent causes of death during diving is entrapment in the cave, until the mixture runs out. In this specific case, I would tend to exclude theentrapment hypothesis: in the Maldives the caves are bright, composed of coral material, so the idea that they got lost is unlikely, especially if we consider that in the group there were two expert instructors who knew the area.
Also the carbon monoxide hypothesis (generated by bad combustion in the compressor that charges the cylinders) is possible but unlikely. In history there have been cases of diving deaths due to intoxication from this compound, but the cylinders had been loaded in closed areas, with awnings blocking the air intakes. Here we are talking about a large yacht and a serious company, with many divers who dived every day without problems. It becomes a minority hypothesis, but it cannot be ruled out until the cylinders are analyzed.
So what could be the most probable hypothesis?
The hypothesis that I consider most likely is that of unexpected current. The alert was yellow, the sea was not good and the currents in that area are strong. The real problem, in my opinion, could have occurred during theexploration: they found one very strong and unexpected current and they struggled to manage the situation.
The current can take you upwards (and in that case maybe you’ll be saved) but also downwards. If you are already 50-60 meters away with the throttle at the limit, it’s like having a Ferrari and driving at 200 km/h on the motorway: you’re safe, but just a little is enough to cause a big accident. They had one mixture to the limitbecause the density was already high, and they had tight deadlinesmaximum half an hour.
Then there is the phenomenon of whiska centrifugal current that takes you up and down: it is possible that one of them, perhaps the younger girl, has inadvertently ended up in the swirl or in a descending current. At that point the group tries to save the person in difficulty: the mother does not leave her daughter and the two instructors do not leave the clients alone. They all end up in the whirlwind, in the current, until the air runs out.
How will the authorities reconstruct the dynamics of the accident?
To reconstruct the definitive dynamics, however, we will have to wait for the analysis of two key elements. The first is the contents of the cylinders: if they find nitrox, then there may have been a technical error in the loading. On the contrary, if they were to find air, the causes would have to be looked for elsewhere.
The second, fundamental element is i wrist computer. From those you print the dive profile and you understand everything: if from the profile you can see that the group remained stationary in one point, then the hypothesis is that of entrapment with asphyxiation. If, however, the computer detects a sudden and deep descent, then it happened as I hypothesized before: the group, or part of them, was caught by the current, dragged downwards, without the possibility of going back up.
