Divemedic

I love how the readers of this blog have such a depth and breadth of experience. Nothing illustrates that more than the SCUBA discussions we have been having. I keep my gear as simple as I can, both because I want to manage the dive, not my gear, and the simpler your gear, the lower the odds for a malfunction. Let me explain my setups:

Buoyancy Compensator

My BC is one I made myself. There was a custom metal shop in Pennsylvania that made custom backplates out of solid stainless steel. The company was called Hammerhead SCUBA. They have since gone out of business. The plate and tank adaptor, pictured below, weigh in at about 12 pounds.

To that, I added a single length of seatbelt webbing wound through the plate, making it into both a waist belt and shoulder straps. On the waist belt, there is a single pouch for adding a single soft weight, so I can use it to adjust buoyancy for things like thicker wetsuits. Also on it are numerous stainless steel d-rings so I can attach various things to my gear when needed.

Also attached to the backplate is an OxyCheq wing with 30 pounds of available lift. They are great wings, and in over a decade of diving, I actually wore one of them out and they let me buy a replacement at 50% off. Great company.

To make things comfortable, I also put a back pad in it. This also created a pocket of sorts that is the perfect place to hide a folding dive flag for when I am on the surface and want to be seen by nearby boats.

Regulators:

I have two Aqualung Legends, one with a DIN connector and one with a Yoke. The yoke connector fits my pony bottle. I also have an older Mares regulator that I sometimes use, there is a DIN fitting on it, and the two DIN regulators I have are tuned so that when you take a good breath on them, they practically force air down your throat. When I am working hard, I want there to be no feelings of being air starved. I have a mechanical pressure gauge on all of them, as well as a QD hose for my dive computer, which allows me to move the computer easily from one regulator to the other, if needed.

Computer

I went through a few computers before I found one I really liked. I tried the wireless ones, and didn’t like them. They lose connection to the pressure sensor too easily. My favorite computer is the Oceanic Pro Plus. Also, it has large numbers that are easier for this old man to read without glasses than is a wrist mount computer. Other advantages are that it allows me to change between three different gas mixes on the same dive. I’ve had great luck with this computer- it served me on hundreds of dives with no issues, including the occasional decompression dive.

Tanks

For tanks, I have a pair of 120 cubic foot high pressure steel tanks, and another pair of 100 foot tanks. I like the 100 foot tanks better. They are 11 pounds negative when full, 2 pounds negative when empty. Using this and a steel backplate enables me to dive without using a weight belt. With this configuration, I am neutral at 10 feet of sea water and an empty tank. Perfect buoyancy. I only accept EAN from companies that blend. I will not use banked EAN because I have had too many issues with contaminated gas from them.

I also have a 19 cubic foot aluminum tank that I use either as an emergency supply or as a deco tank. As a deco tank, I fill it with EAN80, as an emergency tank, it either has air or EAN32.

The rest of it

Completing my setup, I dive with 36 inch freediving fins, because I find that a long stiff fin allows me to drift and steer with little effort but also lets me take advantage of strong leg muscles and really get some speed on. I wear a pair of diving shorts with pockets, so I can store a lift bag and thumb reel with 100 feet of line in one pocket, and a rechargeable flashlight in the other. Attached to my waist belt is a short 4″ dive knife. No snorkel, none of that other extraneous stuff that isn’t really needed, just a simple mask. Too many divers buy a ton of crap that they don’t need, then look like they are wearing half the dive shop while they are in the water. All that does is create drag and weight, which slows you down and causes you to use more gas.

Diving for (Almost) Free

At first, my girlfriend at the time and I used to maintain a website that was a list of dive spots and boats in Florida. We would review all sorts of sites and boats. That’s why my internet handle is divemedic. The site is gone, but it was fldiving.com, and once a boat or shop found out you were running a website for divers, you got all kinds of free stuff. Then my girlfriend and I split up, and I let her keep the website. It lasted a year or two longer, then it disappeared. I guess she didn’t keep up with it.

After that, I spent a few summers working as an underwater dive guide. You don’t make any money at that. What you do get to do is dive for free. Get on the good side of a local dive shop, especially near a tourist area. Florida does some odd things diving that people up north aren’t used to. One of the things we do is drift diving, which other places really don’t do. Tourists want someone to walk them through it, so the dive shop gives them your name and number. They call, and you recommend a boat. There are boats that know my name and offer to let me dive for free if I bring at least three other divers with me. The tourists make the reservation with the boat and pay for their dives and give the boat your name. It doesn’t cost the tourist any extra money for my services, they get a guide who makes sure they have a good time while being safe, and the boat gets some business for the price of an extra diver that costs them nothing. Everyone wins.

When it comes time for the dive, you help them get set up on the boat, then right before we all jump in, I would check their gear to make sure it was setup correctly. After that, all I had to do was throw on the BC and mask, jump in the water, pull on my fins, and I was good to go. This setup is very quick and easy to get into and out of. Fitting these dive trips into my fire department schedule was easy, and I would spend the summer getting in as many as 50 or 60 dives a month. One summer, I hit almost 200 dives from June through August. The most dives I have ever done was a two day period when I did 10 dives between 60-110 feet in just two days. All free.

I would guide my tourist puppies through the dive and get them back to the boat. Sometimes they would tip, sometimes not. I didn’t care. All the tips did was pay for the gas and tolls to get from Orlando to West Palm Beach, Pompano, or Boynton Beach, those being the locations of my favorite dive boats.

The drift diving here is fantastic. The boat drops you on a reef one or two miles offshore, with the bottom being 55-110 feet below, depending on which reef you are diving. For tours, I used to seek out 55-65 foot deep reefs so I could dive it on EAN36 without an issue. The leader (me, when I was the guide) tows a buoy with a dive flag on it using a rope. The divers drift with the current along the reef. You can see a tremendous amount of interesting sea life. At least one or two sharks on every dive- most of the time, you will see even more. Occasionally, you see a really large one- 8 feet or more. During the summer, water visibility can vary from 20 feet all the way up to being able to see the dive boat while on the bottom at 80 feet. On those days, it’s like swimming in a glass of gin.

The limit for the dive is when the first diver in the group hits 700 pounds of gas remaining, a diver hits his NDL limit, or we have been in the water for an hour. I would then have the entire group surface with me. We would spend an hour on the boat, change tanks, then do a second dive. In all, we would spend about 3 or 4 hours on the boat. I would use the rinse hose and some baby shampoo to shower on the back of the boat while we were headed back to shore. Sometimes, I would take a vacation or sick day and spend a week diving every day.

Those were my best days of diving. I spent my summers (this was about 2 years after I divorced my first wife) SCUBA diving. I was great- my tan was awesome. I can see the allure of being a beach bum. It was amazing. I got over 2,000 dives in less than 3 years, averaging more than one dive every calendar day.

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One of the boats used to joke with me, because I once spent over an hour and a half on a 60 foot dive and he was pretty pissed. I pointed out to him that he said “dive the limits of your computer or until you are at your reserve air pressure.” Not my fault I have great SAC, a 120 cubic foot tank, and was breathing EAN36.

After that day, the captain would drop my buddy and me in the water first, motor off some distance to drop the rest of the divers, pick them back up, then come over to get me. He was a nice guy. Near as I can tell, his boat is no longer in business.

During the efforts to recover the bodies of the four divers whose bodies still haven’t been found, one of the military divers has died of decompression illness. As a result of this latest fatality, the Maldives government is suspending body recovery operations until experts in deep and cave diving can arrive on the scene, perhaps tomorrow.

The woman who was the defacto leader of the group is being called an “expert with over 5,000 dives.”

Ms Montefalcone’s husband, Carlo Sommacal, told Italian outlet La Repubblica that his wife was an “expert” and had done 5,000 dives.

I can’t stress how difficult and dangerous this dive is. As I said in the other post, my experience and certifications are remarkably similar to hers, and I am telling you now that I am not, and she is not, in any way qualified to do that dive, nor was she equipped to perform that dive. I know I am not trained or equipped for it. In addition to being NAUI and PADI certified as a divemaster, rescue diver, nitrox, public safety diver, and cavern certified, I am also SSI certified for extended range diving and extended range nitrox. (the first two classes in this list.)

The reports I am seeing is that her group of 5 divers were diving ordinary open circuit with single aluminum 80 cubic foot tanks. That is not the way to do this, and she should know better. It is my belief that Dunning-Krueger is in full effect here- she was making the assumption that all diving is the same, so diving to double the recreational limit is no big deal, and basing that on her training and experience in shallower depths- perhaps thinking her professorship and TV fame made her smarter than everyone else.

The issue with this latest death, is that the Maldives military is no better. It’s being reported in SCUBA circles that the military diver was in recreational gear with single tank and an extra slung aluminum 80. That is nowhere near good enough. The entrance to that underwater cave is at 160 feet. The caverns that are being searched are at 200+ feet.

• There is no safe limit for diving to that depth that doesn’t require decompression.
• Nitrogen is intoxicating at that depth. This compounds the danger, and requires mixed gases, especially as you approach 180 feet or deeper.
• Oxygen in normal air becomes toxic when breathed at depths greater than 185 feet.

For the reasons above, dives to that depth require what’s called hypoxic trimix, a mix of 10-16% oxygen, 50% helium, and the remainder nitrogen. That mixture avoids the risks of OXTOX, narcosis, and lessens the issues with decompression sickness. The issue is that hypoxic trimix can’t be breathed on the surface or at shallower depths. This means a diver has to have what’s called a transit gas, usually trimix with 21% oxygen, to get from the surface to about 150 feet or so. Then there are decompression gases needed, which can include 50% nitrox or other gases. The exact depth for each gas and when to switch depends on the chosen mix, target oxygen pressure (1.2–1.4 atmospheres), Equivalent Narcotic Depth (END), and the decompression plan. The people who do this always use gas and dive planning software. This isn’t the sort of dive where you just dive in and go for it.

In all, a dive like this could require every single diver to enter the water with 4 or more tanks, and still be required to use a surface supplied decompression gas. In many cases with a dive like this, divers will go in ahead of the search team and bring in full tanks of trimix that are left in staging areas within the cave. It’s a very complex and dangerous operation.

Now multiply that by the number of divers you need- this will include the search team, support divers who don’t enter the cave but assist the search team in managing the dive at depths from 150 feet up to the surface, the divers who penetrate the cave to set up staging tanks, then there is a medical team, and other members.

Each diver who enters that cave will have about 25 minutes to conduct the search, then will spend the next two hours working their way to the surface as they decompress at progressively shallower depths. Total run times of 3+ hours are common, with significant stops on 50% nitrox and pure O₂ required to decompress.

In all, an operation like this will take a dozen or more people and cost over a million dollars.

Or you could just cancel the entire useless exercise and leave the dead where they lie. Why risk creating more bodies? My opinion is leave them where they are. They are already dead, and any potential benefit in recovering the bodies isn’t worth losing yet another life. If the Italian government or the family isn’t happy with that, they can mount the expedition, with the understanding that any other death will result in the supervisor of that dive being charged with negligent homicide.

The ocean is an unforgiving bitch if you don’t show her proper respect.

The worst diving accident in the history of the Maldives– 5 people died while on a cave dive to a depth of 160 feet. They died because they were foolish and likely were diving beyond their training, experience, and equipment. Let me explain:

Waves alone were likely not a factor. When you are underwater, you can feel waves to a depth of about 7 times the waves’ height. In order to even feel the effects of waves at 160 feet, those waves would have had to have been at least 23 feet high. That’s not very likely. However, strong winds can cause significant currents around atolls and through underwater caves. That may have factored into this, but no one is talking yet. Still, they had an experienced local dive guide who would be familiar with local conditions with them, so this may not be the case.

More of a factor was depth and the fact that they were in a cave. When you are SCUBA diving, the ultimate safety factor is being able to reach the surface. That’s why new divers are told to always dive with a buddy, because you can share that buddy’s air supply to reach the surface in an emergency. New divers learn all sorts of limits that are intended to ensure you can reach the surface.

When you can’t reach the surface, you are doing what is called “diving in the overhead.” In other words, there is something between you and the surface that is keeping you from reaching it. There are four things that can keep you from reaching the surface. Let’s discuss them:

SAC

The first is the amount of breathing gas you carry. A standard SCUBA tank is filled with 80 cubic feet of compressed air. At rest on the surface, a well experienced diver will breathe half a cubic foot of air per minute. Inexperienced divers can easily triple that, and a diver exerting themselves will also have increased air consumption. That is called your Surface Air Consumption, or SAC.

Depth increases your SAC. Since pressure increases by one atmosphere of pressure every 32 feet of seawater, a person at 160 feet is breathing 5 times the SAC as one on the surface. That 80 cubic feet of air is now going to last only 32 minutes instead of 160 minutes. Add in fear, exertion, and the fact that it will take 3 minutes to get to that depth and 5 and a half minutes to safely ascend from that depth, and now your bottom time is about 7 or 8 minutes, maybe less.

When I was heavily into diving, I would usually dive with 120 cubic feet of gas. At 120 feet, I could get a maximum dive time of about 25 minutes. If they were diving Aluminum 80s at 150 feet, that time would likely have been no more than 14 minutes, and my SAC was excellent.

You are limited from returning to the surface simply because you will drown before you get there if you don’t have enough breathing gas.

No Decompression Limits

Another thing limiting your return to the surface is physiological. Your body absorbs gas while you are breathing it under pressure. Since air is a mixture of multiple inert gasses that are not metabolized, those gasses tend to be absorbed into your body tissues. The principle of these is nitrogen. Once the pressure is relieved by going to a shallower depth, that Nitrogen comes out of your tissues and makes tiny bubbles that expand as the pressure lessens. Think about the bubbles in soda. That’s what is happening. Those bubbles get trapped in places like joints, blood vessels, and various organs and cause all sorts of problems.

To prevent this from happening, divers restrict the amount of gas that is absorbed through limiting the amount of time they spend at depth. The maximum time a diver can remain at a given depth is called the “no decompression limit” or NDL. The definitive table for determining what the NDL is for any particular depth comes from the US Navy. (non-hosted pdf warning) It’s a complex subject, but the NDL for 160 feet of depth is about 7 minutes. If you remain at that depth for longer than this, you can’t return to the surface without decompressing, or you will get decompression sickness.

The NDL can be extended by using gas mixtures other than air. For example, a mixed gas called Nitrox was carried on the boat involved in this accident. Nitrox allows divers to stay down longer because some of the nitrogen in the air is replaced with oxygen. The catch here is that oxygen becomes toxic when breathed under pressure (called oxygen toxicity, or OXTOX). That limits the depth at which Nitrox can be used. The most common Nitrox mixes are EAN32, and EAN36. These contain 32% oxygen/68% nitrogen, and 36% oxygen/64% nitrogen. Neither of those mixes is safe for 160 feet. The maximum oxygen mix you can have at 160 feet is 27%, which is an uncommon custom blend.

Decompression sickness can also be avoided by letting those gasses leech out of your tissues at a slower rate. The easiest way to do this is to return to a shallower depth for an amount of time, to allow them to bleed off. For example, a diver might stop at 30 feet for 6 minutes to bleed off some of the nitrogen he absorbed while at a deeper point before returning to the surface. Many divers do what is called a “safety stop” at the end of every dive, which is in reality a 3 minute decompression stop at 15 feet.

For various reasons, most divers don’t use tables to compute all of this. Instead, they wear computers that constantly compute the amount of gas in your tissues and advise you on how long you can stay down, and if you violate that limit they will make recommendations for decompression stops.

Physical barriers

The next barrier to reaching the surface is a physical one- diving in a location where there is a literal thing between you and the surface. That can be inside of a wreck, or in a cave. The hazard here is that it is easy to become disoriented or lost inside of one of these, and you are trapped and unable to find your way out. It takes different procedures, training, and equipment to enter a wreck or cave.

This incident

From diving oriented publications:

Though the dive-group were said to have entered the water in the morning, the alarm was raised only at 1.45pm, suggesting that they might have been prepared for a long, deep dive. Details have yet to be released about the equipment they were using.

Other reports indicate that the weather may have caused strong currents, which could have contributed. No information has been given about the precise cause of the fatalities, although some media reports have made references to oxygen toxicity and gas mixture problems.

Accidents

I have been present for several diving accidents, and I have known several people who have died SCUBA diving. I have also read hundreds of reports of SCUBA accidents. In each and every case of which I am aware, the accident was caused by a diver who went into a situation for which they were not:

• experienced
• equipped
• or trained

Or some combination of those three. That appears to be the case here. A dive inside of a cave, at a depth of 160 feet is beyond the training and experience of recreational diving. It’s called a technical dive, and these require a lot more training and equipment than most divers have.

Dives that go into more complex environments have to be planned. The deeper you go, the longer you stay down, and going into a cave or wreck all require much more planning than a simple 60 foot open water dive.

When diving in an overhead environment like this, the rule of thumb is take enough gas so where you have 1/3 of it in reserve when you reach the surface. For this dive, that would mean about 100 cubic feet of gas, but more like 110 cubic feet to be safe.

On top of this, the Maldives limits recreational diving to no more than 100 feet in depth.

This tragedy was a case of divers going beyond their limits, as most dive accidents are. Diving is a safe sport, as long as you follow the safety rules. Too many divers get tempted to push just a little beyond the limit, and that’s when tragedy strikes.

That is reportedly the case here, even though it isn’t a reliable source, the dive community is saying they were diving on recreational open water equipment, which seems to solidly point towards diver error.

The ocean can be an unforgiving bitch if you don’t respect her.

On the gripping hand

Other than diver error, there is also the possibility that their air was contaminated. Breathing in carbon monoxide, or air contaminated with compressor oil can be deadly. I once dove with Nitrox that was contaminated with compressor oil. I got a buzz from it at 50 feet and had to abort the dive. It cost me several hundred dollars to get all of my equipment cleaned for oxygen service. I never returned to that dive shop.

So there are other possibilities, but the smart money is on diver error.

My training

I have over 4000 logged dives, and I don’t know how many unlogged ones. I am a Master Diver and served on a Rescue Dive team for a number of years. We mainly did body and evidence recovery. The majority of my logged dives were from 60-120 feet, with my deepest dive being a 180 foot dive in Mexico. I’ve done a number of wreck dives, and a few caverns and caves. Caverns and caves just don’t interest me, it’s just a bunch of rocks. Boring.

I was just beginning to get into tech diving when I stopped diving. I had just completed extended range nitrox and was looking into doing trimix. Sadly, it became harder and harder to find others to dive with, so I went no further. My last dive was about 6 years ago.

I’m not going to say that I never broke the rules. I was just lucky enough not to get dead. I once went SCUBA diving in a hurricane. Well, the edge of a hurricane. We thought we would sneak a dive in, in between squall lines. That was one of the scariest dives I have ever done, and I learned an important lesson about the unpredictability of currents when the weather turns bad. Still, I got off lightly. All I wound up losing was a fin strap and the flooding of a $1200 underwater camera.