Training

Data Driven

One of the things I am drawn to, and quite skilled at, is processing data. It’s why I enjoyed operating a fire truck, and it’s also why I like my job in medicine and enjoy the technical end of SCUBA. I would probably been pretty good at engineering. I love processing data and doing math in my head. I also enjoy having a good tool that will make that job easier.

Enter dive computers. These machines take all of the guesswork out of diving. Traditionally, divers would use a table where the maximum depth and total dive time were looked up on a table that would tell you the maximum time you could be underwater. This is called “square profile” diving. The table assumes you descend from the surface to a set depth, remain at that depth the entire dive, then return directly back to the surface. In reality, no one dives like that.

A dive computer uses a mathematical model to calculate how much Oxygen (and other gases) are in your tissues, then uses that to tell you what you need to do in order not to get the bends. It resamples the factors of the dive every 30 seconds.

That’s one of the things that I can’t understand about this diving accident. The diving computer would have warned them:

  • that they were approaching the no decompression limit once they had been under for about 7 minutes at a maximum depth of 160 feet. It would beep and flash.
  • When they reached 187 feet, they would have gotten another set of beeps warning them that the oxygen was at the maximum safe limit of 1.4 atmospheres of pressure
  • Most computers have a depth alarm that would have warned them about exceeding depth limits
  • Many computers have turnaround alarms that will warn you when you have used a third (or some other programmable amount of your air) of your breathing gas
  • Many dive computers would have had their models exceeded and would go into “violation” mode. There are more alarms here, and the computer only functions as a digital set of gauges after that point.

In short, there is no way that dive was an accident, and that is not even considering the stupidity of swimming that far into a cave. It always astounds me that someone will pay a thousand dollars for an expensive piece of gear that’s designed to save your life, then will ignore that device. The cheapest dive computer can be bought for less than $100 (although I wouldn’t bet my life on cheapest.)

My dive computer cost me well over $600, but it is obsolete and no longer for sale. If I were to buy one today, I would want a gas integrated console computer that can handle multiple gas mixes on one dive. The small wrist ones aren’t readable by this old man’s eyes- the numbers are too small on the display and I don’t want to wear a prescription dive mask.

So with that being said, I would want:

  • gas integrated
  • nitrox capable to 100%
  • multiple gases on one dive

With that, I my research settles on these:

  • Apeks DSX Dive Computer:The nice thing about this one is it would let me upgrade to trimix if I decide to do that in the future. It’s pricy though: $1200. Also, the connection to your tank is wireless, and that means sometimes losing the signal and not knowing how much pressure you have left.
  • Mares Genius: This one is cheaper at $800. Still has the wireless connection issue.
  • Oceanic Pro Plus X: This one solves the wireless issue, but it only handles nitrox to 50% and can’t do trimix. It’s also pricy at $1200.

I’m sure there are others, but those are the ones I would consider.

The disclaimer: I don’t advertise, and receive nothing for my reviews or articles. I don’t think that I ever will. I have no relationship with any products, companies, or vendors that I review here, other than being a customer. If I ever *DO* have a financial interest, I will disclose it. Otherwise, I pay what you would pay. No discounts or other incentives here. I only post these things because I think that my readers would be interested.

By Divemedic, ago

Answers

From la Repubblica, a story of the deceased divers from the Maldives. A Finnish team managed to recover the final two deceased divers yesterday. All four of the remaining divers were located in the same chamber, more than 200 feet below the surface, and more than 300 linear feet inside the cave. The rescue team has given some insight into what happened to the missing divers. To understand what happened, a map of the underwater cave.

This is a diagram of the cave system, as seen from above, looking down. The divers entered the cave from the right, off of the frame.

The divers entered the cave system at a depth of 180 feet. The cave begins with a first large, very bright cavern with a sandy bottom. It would seem enticing to go further, as this looks very inviting.

They swam through a connecting tunnel from the first chamber to the second. This connecting tunnel is almost 100 feet long, ten feet across, and just three feet tall. It led to the second chamber of the cave, which is a large, round space with no natural light. This second chamber had a depth of over 200 feet. The interior of this chamber would be completely cut off from daylight, and the only visibility would be provided by any handheld lights that the divers had brought with them. The inside of such a chamber is a confusing jumble of rocks, with one rock looking much like any other rock. Even though the water in here was clear, it was a dark, confusing maze of rocks and sand.

At some point, they entered the third chamber (which was a dead end with no way out) through another tunnel whose entrance was right next to the connecting tunnel leading back to the first chamber and the exit. The Finnish team notes that the exit tunnel’s opening was partially obscured from view from the vantage point of a diver in the second chamber by a large pile of sand. It is easy to get over the sandbank into the second chamber, but when you turn around to leave again the bank almost looks like a wall, hiding the corridor from view. The team believes that the divers mistook the tunnel leading to the dead end and their literal death for the tunnel that would lead them to safety.

The divers were only equipped with 80 cubic feet of breathing air. At 200 feet, they would breathe through that supply at 7 times the rate of the surface. By the time they had penetrated the cave to that point, they likely had a minute or two of air left before they all drowned from lack of air.

This reinforces my opinion of what I think happened. These divers were diving beyond their training, experience, and equipment. Had they been properly equipped and trained, they would have stretched a guideline as they went and wouldn’t have gotten lost. They would have had more than just 80 cubic feet of breathing gas, and they wouldn’t be dead.

This was diver error, plain and simple. As I said before, the ocean is an outright jealous bitch, and she shows no mercy to those who do not give her the respect she deserves.

EDITED TO ADD

One of the things that gets me, although it shouldn’t at this point, are the social media experts who are claiming this team had tons of training and experience, so something else must have happened. I have seen theories ranging from “they had bad air” to rogue currents (although how a current runs through a dead end cave, they don’t explain), and even one that claims they were drug there by a large squid to be used as food.

I am not the only experienced diver who actually knows better. It doesn’t take any special disaster to have made this happen- just a combination of inadequate training and experience combined with arrogance of Dunning Krueger and a dangerous environment with a very small margin of error, and that’s all you need.

By Divemedic, ago

The Next Chapter

The SCUBA tragedy in the Maldives has another interesting turn, and one that actually supports my belief that the divers were diving far beyond their training, equipment and experience. The bodies of the four missing divers have been recovered, and they were located in the third chamber of the cave at a depth of 200 feet.

The Italian tour operator that manages the Maldives diving trip denied authorizing or knowing about the deep dive that violated local limits, its lawyer told Italian daily Corriere della Sera on Saturday, according to an AP report.

Orietta Stella, representing Albatros Top Boat, said the operator “did not know” the group planned to descend beyond 30 meters. Crossing that threshold requires special permission from Maldivian maritime authorities and the tour operator “would have never allowed it,” she said.

I want you to look at this short video of the equipment that the dive team is using to recover the bodies.

This setup is called a rebreather. It works by having the diver rebreathe the air in his lungs over and over again. The device removes CO2 from the exhaled air and adds oxygen as needed to maintain a safe mixture. These devices are the gold standard for diving at the edge of human physiology. This is closed circuit diving, and rebreathers are specialized equipment, costing tens of thousands of dollars for each.

Now consider what the divers who died were equipped with:

The Italian divers were experienced, but the equipment used appeared to be standard recreational gear rather than technical equipment suited for deep-cave diving, she said.

This is the part that I can’t confirm, but this is reportedly the cave where the group was diving. Even if it isn’t the exact same cave, this is what it would look like. These caves are covered in fine silt, and one wrong move, one errant fin kick sends that silt up into the water of the cave, reducing visibility to zero.

One of the things you do in an area where visibility is potentially poor is use guidelines. A guideline is a rope that leads you back to the exit. Firefighters, rescue personnel, and cave divers are all familiar with this. The line has markers on it to indicate direction so you don’t accidentally follow the line in the wrong direction. It looks like this:

The round markers are called cookies, and the arrows are called, well, arrows. These shapes are easy to identify by feel in cases where there is no visibility. The arrow is placed on the line so it points to the exit. Unlike arrows, which explicitly point toward the nearest exit, cookies are round and do not point anywhere. They are used to mark other things. For example, if a cave branches off in different directions, the guideline will as well. So you use a cookie to mark which of the guidelines the team followed to go deeper into the cave.

In this case, it is evident that the divers didn’t use guidelines. They weren’t equipped for deep or decompression diving, and none of the divers involved were trained for this.

When that visibility is zero, you are weightless, it’s very disorienting. If you don’t know what you are doing in a cave, this is a death sentence. You have about 3 minutes to figure it out, or you and everyone with you in this cave is dead. That’s how 5 divers can die all at once. My guess is that this is what happened, and one of the divers managed to make it as far as the cave entrance before his air ran out. This has been my belief all along, and nothing I have seen to date contradicts my belief.

Now that the bodies have been located, the plan is to recover two of them tomorrow, and the final two on Wednesday.

By Divemedic, ago