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Why Do Divers Run Out Of Gas?

Not surprising, the answer is more complicated than simply, they neglected to look at their gauges. Here Aussie diving medical researcher and former editor of DAN’s Annual Diving Report, Peter Buzzacott dives into several deep datasets including DAN’s Incident Reporting System (DIRS) and nearly four decades of cave diving incident data, to tease out some insights on gas emergencies and get a handle on the risks. Don’t stop those S-drills!

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by Peter Buzzacott

See companion story for a guestimate of the risk: What is the Risk of Running Out of Gas?

Next year it will be 30 years since I first learned to dive. At the time, I had no idea that diving would occupy such a large part of my life. I distinctly remember kneeling on the sandy bottom end of the Great Barrier Reef, sharing a regulator with my buddy, and seeing sunlight rippling down through crystal clear water. On one of these “confined water” dives we had to swim horizontally for 10 m/30 ft holding our regulators out of our mouths and blowing a steady stream of bubbles. This wasn’t as easy as it sounds and we had to ration our bubbles to make it the whole way. Then, on an open water dive, the instructor took turns holding us with one hand and gripping a rope with the other while we took a breath, took the second stage out of our mouths, and then went for the surface, breathing out all the way. Up, down, up, down, the instructor went, with each student—one at a time. 

Courtesy PADI Worldwide. Copyright 2021, used with permission.

Most of today’s recreational dive courses do not include buddy breathing, they teach gas sharing with an alternate air source (AAS). Even before COVID-19, the buddy breathing skill had disappeared from most recreational training programs. The controlled emergency swimming ascent (CESA) has also disappeared from some programs. 

When I became an instructor, I made many hundreds of these but, now that I think about it, I don’t recall ever seeing anyone actually make one for real after running out of gas. These days everyone dives with two second stage regulators. In technical diving, we even dive with at least two cylinders; so, I wonder, do technical divers run out of gas and, if they do, then why?

What Do The Experts Say?

Some years ago, I asked a panel of 27 diving experts a similar question regarding recreational divers in general.1 The panel consisted of nine diving/hyperbaric doctors who had treated hundreds of injured divers; nine expert dive guides, most of whom were instructors; and nine expert recreational divers who had dived all over the world and written hundreds of feature articles for dive magazines. 

At the time, I suspected divers mostly ran out of gas because they didn’t pay attention to their gauge. But, to my surprise, the experts suggested about 20 reasons, such as diving deeper than usual, diving in a current, not wanting to end the dive for their buddy, using a smaller tank than their buddy, being underweighted, and many others, all of which sounded plausible. 

I sent the whole list of potential causes back to the group and asked them to rank, in their opinion, the five most likely causes. Then I gave five points to everyone’s most likely potential cause, four points to the second most likely, and so on. I added up all of the points and then ranked all the causes according to the total score. Then I sent this ranked list back to the group for one last review and asked them to consider the “weight of opinion” from the group as a whole, and to reconsider their top five reasons. 

As an expert panel, the group moved toward consensus. Just as I’d suspected, failing to monitor the gauge was the number one proposed potential cause of running out of gas, followed by inexperience, overexertion, inadequate training, and poor dive planning. Other than perhaps an unexpected current or underweighting leading to overexertion, the proposed reasons leaned toward human factors rather than the other two types of factors in the classic diving injury causal triad—those being environmental factors and equipment factors (Figure 1).2,3,4

Figure 1: The classic diving injury causal factors triad 2,3,4

The process I’d followed to gather expert consensus of opinion is called a “Delphi” process, which was originally developed by International Business Machines Corporation (IBM) to make forecasts on matters about which there was considerable uncertainty i.e. where there is little data. Opinions aren’t solid evidence; however, they can point towards a direction worth investigating. 

Next, I visited Divers Alert Network(DAN) as an intern and worked on an analysis of diving fatalities within a subset of technical divers—cave divers. More on that later, but while there, I had the opportunity to examine a large dataset of recorded dives from Project Dive Exploration, headed by Drs. Richard Vann and Petar Denoble. 

The dataset we had at that time revealed over 50,000 dives recorded by more than 5,000 recreational divers, (including an unknown number of technical divers). We examined these data in two ways. First, to control for environmental and equipment factors, and to focus on demographic (or human) factors, we counted each diver just once and compared those divers who had reported running out of gas, (during any recorded dive in that dataset), with divers who had not run out of gas. Surprisingly (to me), having run out of gas was more common than expected among older females (males were more likely to report other problems, like rapid ascent). 



Next, to control for the human factors, we looked at just the dives made by divers who had made both at least one dive where they ran out of gas, and at least one dive where they did not run out of gas. I wanted to know what it was about those dives that might have caused the divers to run out of gas. Well, it turned out the out-of-gas dives were deeper, shorter (probably because they were deeper), often made from a live-aboard or charter boat, and involved a higher perceived workload.5 Hmmm… Perhaps overexertion was a factor after all.

After returning to Western Australia to undertake a PhD researching this, I spent the next few years recording 1,000 recreational dive profiles made by 500 divers. I recorded their start and end pressures, tank size, and noted factors such as current, how they felt their workload was (resting/light, moderate, or severe/exhausting), how many dive experiences they had, and what previous dive training they had completed. For the analysis, dives made by divers who exited with <50 bar/725 psi of pressure (needle in the red zone, n=183) were compared with other dives recorded at the same time at the same dive site (n=510) by divers who exited with >50 bar/725 psi pressure remaining (needle not in the red zone). 

Ending a dive low on gas was correlated with younger males with a longer break since their last dive, fewer lifetime dives, at deeper depth, and a higher rate of gas consumption (adjusted to an equivalent surface air consumption (SAC) rate, for comparison between dives made at different depths). Perhaps more tellingly, compared with 1% of the dives with >50 bar/725 psi at the exit, 11% of the low-on-gas divers reported being surprised at the end of the dive by how low their remaining gas pressure was.6 A more detailed analysis of the average workload associated with recreational diving, using this same dataset, identified that higher perceived SAC rate was not associated with sex but was associated with older age, lower dive certification, fewer years of diving, higher perceived workload, and other factors.7 

Technically Out of Gas

Returning to the topic of technical diving, a colleague and I re-examined the DAN cave diving fatality reports collection that I had worked with as an intern, and this time we concentrated on the previous 30 years of data: 1985-2015. Dividing it into two equal halves which we referred to as the “early” and “late” groups, reading each report carefully, and using a reliable cave diving fatality factors flow-chart previously developed,5 we classified factors associated with each cave diving fatality and then compared the two groups. 

In the late (more recent) group, the proportion of cave divers who were trained in cave diving had significantly improved, perhaps due to increased awareness of the need for proper cave diver training before entering a flooded cave. The majority of the 67 trained cave divers in our dataset were diving with two cylinders on their back (doubles), and the late group was diving further into the cave than the early group. Of the 67 trained cave divers, 41 (62%) had run out of gas. Looking at the five “golden rules” of cave diving, the “rule of thirds” was the most common (n=20) rule that was suspected to have been broken by the trained cave divers: the most lethal.9

So, it would seem that some technical divers do run out of gas, though thankfully that appears rare. We should bear in mind that cave divers may differ from other types of technical divers in their procedures, demography, and equipment; their environment (by definition) certainly differs from that of wreck divers. 

Currently, I know of no ongoing research into out-of-gas incidents among technical divers, other than the current Diving Incident Reporting System, hosted by DAN. An analysis of the first 500 reported incidents recently examined every incident—recreational and/or technical—during which the diver ran out of gas.10 The sample (n=38) was divided into two groups: those who made a controlled ascent (e.g. on a buddy’s donated regulator) and those who made rapid ascent (e.g. a bolt to the surface). 

Among divers who reported having run out of gas, but survived to report the incident, 57% of the rapid ascents resulted in a reported injury. Among the 24 controlled ascents, just 29% reported an injury.10

Among divers who reported having run out of gas, but survived to report the incident, 57% of the rapid ascents resulted in a reported injury. Among the 24 controlled ascents, just 29% reported an injury.10 This modern finding is in line with the statistics reported 27 years ago by Dr. Chris Acott when he analyzed more than 1,000 diving incident reports. Examining 189 out-of-gas incident reports, Dr. Acott found 89 made a rapid ascent, and 58% of those reported an injury. Among the 79 controlled ascents, only 6% reported an injury.11 

Table 1 shows the total number of dive incidents in each category, after adding both studies together. It seems to me that, while we have moved on from buddy-breathing and the controlled emergency swimming ascent, in the last 30 years the problem of running out of gas has not gone away. 

No Injury
(row %)
Injury
(row %)
Total
(col %)
Non-rapid ascent 91 (88)12 (12)103 (50)
Rapid ascent43 (42)60 (58)103 (50)
Total134 (65)72 (35)206 (100)
Table 1: Injuries among 206 out-of-gas dive incidents by ascent rate10,11

In conclusion, the evidence confirms what we all know: running out of gas is associated with diving injuries and fatalities. It appears that the level of correlation of demography information (like age and sex) with out-of-gas incidents may depend upon the study design, the pool of divers studied, and/or the specific potential causes of running out of gas being investigated. For example, in one study, older females were more likely to self-report out of gas problems; in another study, young males’ remaining gas was measured and observed to be low. In yet another study, SAC rate increased when perceived workload increased, regardless of sex. 

Therefore, I’d suggest it is prudent to consider everyone potentially at risk of running out of gas and, in order to mitigate this risk, both recreational and technical divers should be proficient in gas planning and monitoring their remaining gas, regardless of age and/or sex. 

[Ed.note—Most agencies today require some level of proficiency in managing emergency out of gas scenarios. For example, GUE requires divers at all levels to train regularly for this eventuality. This training also emphasizes gas management strategies like “minimum gas reserves” and the related “one third” rule to ensure divers always have enough supply to share gas aka buddy breathe from any point in the dive, and all the way to the surface. Violation of these strategies risks insufficient gas in all environments.]

Influencers

The influence of workload is interesting, and technical divers who perceive an elevated workload may well remember that this has been associated with both higher rates of gas consumption and unexpectedly running low on gas. So, when detecting a current or perceiving an elevated workload, I recommend keeping a closer-than-usual eye on the remaining gas and, if a current is suspected before the dive, then plan for an elevated SAC rate. 

The influence of training/certification consistently appears to be associated with the risk of running out of gas, as does having made fewer lifetime dives. Highly trained and experienced divers might bear this in mind when diving with buddies who are newer to our sport. Offer them opportunities to gain experience and recommend additional training when they are ready. We were all inexperienced once.

Technology has improved in recent years; for example, tank pressure transponders are more reliable today than ever before. It is possible that in the future these resources, coupled with audible alarms, may prove to be highly effective at preventing technical divers from running out of gas. Until we know how effective such alarms are at preventing out-of-gas dives, our best course of action is to dive within the limits of our training and experience, and to keep an eye on our remaining gas. 

See companion story for an estimate of the risk: What is the Risk of Running Out of Gas?

Do you think that it could it happen to you?

References

1. Buzzacott P, Rosenberg M, Pikora T. Using a Delphi technique to rank potential causes of scuba diving incidents. Diving and Hyperbaric Medicine. 2009;39(1):29-32.

2. Edmonds, C. and Walker, D. Scuba diving fatalities in Australia and New Zealand: The human factor. SPUMS J. 1989;19(3): 94-104.

3. Edmonds, C. and Walker, D. Scuba diving fatalities in Australia and New Zealand: The environmental factor. SPUMS J. 1990;20(1): 2-4.

4. Edmonds, C. and Walker, D. Scuba diving fatalities in Australia and New Zealand: The equipment factor. SPUMS J. 1991;21(1): 2-5.

5. Buzzacott P, Denoble P, Dunford R, Vann R. Dive problems and risk factors for diving morbidity. Diving and Hyperbaric Medicine. 2009;39(4):205-9.

6. Buzzacott P, Rosenberg M, Heyworth J, Pikora T. Risk factors for running low on gas in recreational divers in Western Australia. Diving and Hyperbaric Medicine. 2011;41(2):85-9.

7. Buzzacott P, Pollock NW, Rosenberg M. Exercise intensity inferred from air consumption during recreational scuba diving. Diving and Hyperbaric Medicine. 2014;44(2):74-8.

8. Buzzacott P, Zeigler E, Denoble P, Vann R. American cave diving fatalities 1969-2007. International Journal of Aquatic Research and Education. 2009;3:162-77.

9. Potts L, Buzzacott P, Denoble P. Thirty years of American cave diving fatalities. Diving and Hyperbaric Medicine. 2016;46(3):150-4.

10. Buzzacott P, Bennett C, Denoble P, Gunderson J. The Diving Incident Reporting System. In: Denoble P, editor. DAN Annual Diving Report 2019 Edition: A Report on 2017 Diving Fatalities, Injuries, and Incidents. Durham (NC): Divers Alert Network; 2020. p. 49-67.

11. Acott C. Diving incidents – Errors divers make. Safe Limits: An international dive symposium; 1994; Cairns: Division of Workplace Health and Safety.

12. Buzzacott P, Schiller D, Crain J, Denoble PJ. (2018). Epidemiology of morbidity and mortality in US and Canadian recreational scuba diving. Public Health 155: 62-68. 

13. Buzzacott P. (editor) (2016). DAN Annual Diving Report 2016 Edition: A report on 2014 data on diving fatalities, injuries, and incidents. Durham, NC, Divers Alert Network

14. Buzzacott P (editor) (2017). DAN Annual Diving Report 2017 Edition: A Report on 2015 Diving Fatalities, Injuries, and Incidents. Durham (NC), Divers Alert Network.

15. Buzzacott P and Denoble PJ. (editors) (2018). DAN Annual Diving Report 2018 Edition: A report on 2016 data on diving fatalities, injuries, and incidents. Durham, NC, Divers Alert Network

16. Denoble PJ. (editor) (2019). DAN Annual Diving Report 2019 Edition: A Report on 2017 Diving Fatalities, Injuries, and Incidents. Durham (NC), Divers Alert Network.

You can add a diving incident to the DAN database by name or anonymously here: Diving Incident Reporting System (DIRS).


Dr. Peter Buzzacott MPH, PhD, FUHM, is a former PADI Master Instructor and TDI Advanced Nitrox/Decompression Procedures instructor, having issued >500 diver certifications. Today he is an active cave diver, holding various advanced cave diver certifications including advanced (hypoxic) trimix diver, and he is gradually gaining experience with CCR diving. To finance this, he conducts research into diving injuries and decompression/bubble modeling at Curtin University in Perth, Western Australia.

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Hal Watts: Plan Your Dive

Known for his deep air diving exploits back in the day, 86-year-old Hal Watts, aka “Mr. Scuba,” is one of the pioneers of early scuba and credited with coining the motto, “Plan Your Dive. Dive Your Plan.” He founded the Professional Scuba Instructors Association International (PSAI) in 1962, which eventually embraced tech diving, but never relinquished its deep air “Narcosis Management” training. Italian explorer and instructor Andrea Murdock Alpini caught up with Watts and teased out a few stories from the training graybeard.

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Interview by Andrea Murdock Alpini 
English text by Vincenza Croce

Hal Watts, Terrence Tysall, and Bill Stone in March of 1993.  This was the last stop in the U.S. for a test dive of the Cis-Lunar Mk-4 rebreather prior to Stone’s San Agustin expedition (1994) for its first real sump dive.

“Plan your dive, dive your plan,” is a common refrain in diving, but it’s easy to forget the meaning of this phrase has changed over time.

The underwater explorers of the early days learned to plan their dives with watches, depth gauges, and US Navy tables. Back then, decompression tables were the Bible for divers—something miraculous, halfway between alchemy and physiology. Those trail-blazing divers defined what it meant to “plan” a dive.

But, at the time, the term “technical diving” did not exist; divers breathed air on the bottom as well as during decompression. Only after many years was oxygen added, followed by the famous jump into the hyperbaric chamber.  

Later came new innovations after a few decades of experiments: hyperoxygenated binary mixtures, the NOAA tables, Heli-air (i.e. the addition of helium in tanks loaded with air), the change in the speed of ascent, new molecules to be studied, new physiological and narcotic effects, and their consequent impacts on humans and their psyches.

In a very short time, diving traditions underwent a metamorphosis. The spool and the coral tank became a proper reel, the ascent bin and the plastic bag disappeared in favor of the buoyancy control device (BCD), the surface marker buoy appeared—and then, even later on, wrists were adorned with underwater computers instead of decompression slates.

Divers later renewed and revolutionized a niche discipline, transforming it into a sporting phenomenon and a vocation. Faced with imminent change, there is often nothing that can be done when an anomalous wave arrives; you cannot stop its irresistible force with the wave of a hand. And thus was the American revolution of underwater technique, where the means of exploration—read mixed gas and scooters—have become the end.

The self-proclaimed originator of the “plan your dive, dive your plan” motto was 86-year old Hal Watts, the founder of American didactic Professional Scuba Association International (PSAI) and a diving pioneer who once held the Guinness Book of World records for deep diving. Though the use of trimix grew in popularity, Hal continued to believe in deep air, in the ancient technique of coral fishermen. He supported wreck and cave diving—with decompressive mixtures and new configurations through PSAI; but, above all, he believed (and continues to believe) that deep air, if properly practiced, is a discipline with unique logistics, hidden dangers, and irresistible charms that can take you to a parallel world.

Hal Watts speaking at aquaCORPS tek.93 Conference

First of all, Hal, what was the dive that changed your way of seeing scuba diving? I mean, a dive that was like an epiphany, a dive which changed your point of view on a technical matter?

Hal Watts: Wow, you sure are really trying to test my old man memory. Now I’ll have to review some of my old logbook entries. 

The first scuba dive that really got my attention as to just how serious and dangerous scuba diving can be was on December 2, 1962. I was diving with Bob Brown, co-owner of Florida State Skindiving School in Orlando, Florida. I was a member of a dive club in Orlando known as Orlando Sport Diving Club. Bob and I had heard of a sinkhole in Ocala known locally as Zuber Sink as well as Blue Sink. Years later, I later leased the property and renamed it as Hal Watts’s 40 Fathom Grotto, and I eventually purchased the Grotto in mid-1979.

We had never talked to anyone about the sinkhole; therefore, we had no idea about the visibility or the depth. Up to this point, I had constructed my favorite BCD, using a large white Clorox plastic jug, which we tied to our twin tank system. We put air into the BCD from our “Safe Second Stage” mouthpieces. 

Bob and I tied our safety line to a tree on the bank of the sink and reviewed our dive plan. I am reminded of the motto I came up with, many moons ago—Plan your dive, dive your plan. 

We all know that motto. I didn’t realize that it was you who coined it.

It was back in the 1960s when I was writing course manuals for NASDS [National Association of Scuba Diving Schools] and opened up my Mr. Scuba dive shop.

Mr. Scuba’s Magic Bus!

But back to the dive at Zuber. I’ve failed to mention the fact that neither of us had been doing any dives below 30 m/100 ft. We followed the cave line down slowly, not paying enough attention to our depth. Before we realized it, we had hit the bottom, stirred it up, and had no clear water.

Lucky for us, I kept the cave diving reel in my hand, and Bob kept his hand on the line. I couldn’t see; however, I could feel Bob’s hand, squeeze his fingers tight on the line, grab his thumb, and give it the “thumbs up” signal. I don’t know how we managed it, but we were both able to use our NASDS safe second stages and add air into the Clorox “BCDs.” We were actually fated to begin an uncontrolled, too-rapid ascent. All of a sudden, we hit an overhead wall, which stopped our ascent at a depth of 9 m/30 ft. 

We looked at each other, and gave the OK hand signal. While decompressing, following the old Scubapro SOS mechanical computer, I started to pull up the loose line until the dive reel appeared. Wow, we sure had an awful lot of loose line floating around us. Were we extremely lucky? Of course, we were. Our problem was that we never planned our dive, and consequently, were unable to dive a plan.

After that dive, I worked with Scuba Pro and Sportsways to create the “Octopus,” or “safe second.” A while later, the octopus appeared for the first time in Scuba Pro catalogs. I was also the first to add a pressure gauge along with the Octopus.

Hal Watts set the world deep air record to 120m/390 ft in 1967

Ah yes, the “Safe Second.” That’s what NASDS called backup second stages, right? Sheck Exley (1949-1994), the legendary cave explorer with whom you were friends, was also credited with fitting a redundant second stage reg with a necklace. I want to ask you more about Exley, but first, I want to know: What are the best wrecks you ever dived?

This is really very hard to answer. I’ll have to list four, in the order that I dived them: the USS Monitor, Andrea Doria, Japanese wrecks located in Truk Lagoon, and the Lusitania in Ireland.

The most important would have to be the USS Monitor, a submarine used during the Civil War. A group of well-known USA divers applied to the National Oceanic and Atmospheric Administration (NOAA) for a permit to dive the Monitor, as she was located in protected waters. In addition to myself, the group consisted of: Gary Gentile, attorney Peter Hess, and several other well-known expert divers. At first, NOAA refused. Then, Peter Hess filed proper papers asking that we get the NOAA permit. To that end, we presented my Deep Air training material to the concerned NOAA group. I appeared as an expert witness and provided NOAA staff and their legal representatives with my internationally accepted training material and my record of training several world record deep air divers. Our deep air training has been accepted worldwide with zero diving deaths. After that, we received the permit. 

Other than the Monitor, my favorite deep wreck dive would be the Lusitania, which is a very personal and proud story for me. The main reason is because venture capitalist Gregg Bemis owned the diving rights to the Lucey at the time. Gregg had contacted me requesting that I train him on PSAI Narcosis Management Level V, on air—which is 73 m/240 ft—and then train him on trimix so he and I could dive to 91 m/300 ft on the Lusitania lying off the coast of Ireland. 

When word got out that I had enrolled Gregg in my Narcosis Management Course, a well-known international course director (a personal friend of mine) called and told me, “Hal, do not teach Gregg deep diving.” 

PSAI’s ad in aquaCORPS Journal circa 1994 offering deep air training.

He told me that he had been training Gregg at his facility, and that he was a “train wreck.” “He is from a very well-off family in Texas, and if you cause him any injuries, you will be sued and put out of business,” my friend said. Well, guess what? Gregg completed the 240 Level V Deep Air course, then our PSAI Trimix course. My wife, Jan Watts, Gregg, and I went to Ireland to dive the Lusitania. He and I made an awesome 91 m/300 ft trimix dive to the deck.

Diving on the Andrea Doria with Tom Mount, Peter Hess, and several great wreck divers was also an awesome dive. Last but not least was a great trip to Truk to dive on some of the Japanese wrecks.

Please tell us about Sheck.  What was your relationship with him like?

Sheck and I became friends and made several dives together, and one of my favorites happened when Sheck, his Mary Ellen, my wife Jan, and I were diving at 40 Fathoms. Sheck wanted to practice gas switches during descents. Sheck was practicing, getting ready for a planned very deep dive (I think in Mexico with Jim Bowden). The four of us swam to the east side of The Grotto, slowly following the wall during our controlled descent, watching Sheck practice gas switching. 

Sheck Exley and Hal Watts at a NSS-CDS conference

After reaching our planned depth of 73 m/240 ft, we began our controlled ascent up to our first planned deco stop. During our last deco stop on our 4.5 m/15 ft platforms, I noticed that Sheck had a funny look on his face and was messing with his drysuit between his legs. I remembered then that he had told me that he had an attachment installed in the drysuit that would allow him to pee underwater. He was clearly in a bit of discomfort and Mary Ellen, Jan and I just floated nearby and watched.

I’ve heard that Sheck later used diapers, or just cut it loose in one of his old neoprene drysuits on his big dives, so evidently he didn’t get that early p-valve to work. What about your friendship and job collaboration with Gary Taylor, your brother-in-arms and a co-owner of PSAI?

Andrea, get comfortable, since this question will take some time to properly answer.

I first met Gary in Miami, which is where we became friends when I was staying in his home and taking Tom Mount’s nitrox course.  I have a photo of Tom, Gary, and me gas blending on the floor of Tom’s garage. During the course, Tom was still using his worn-out hand written paper flip charts as his notes.

Gary was impressed with my deep air program and offered to put together an updated slideshow presentation for me to teach with. PSAI still uses an updated version of this system to date. Gary stayed with Tom until Tom thought he had sold IANTD [International Association of Nitrox and Technical Divers] to another individual. After that sale came about, Gary contacted me wanting to get more involved with PSAI. Being smarter than folks thought I was, I jumped at the chance to have Gary on the PSAI Team. Tom’s deal fell through, but Gary was totally involved with PSAI, and now is a partner and president of our agency. Thanks to Gary and Tom. 

Many, many years ago I was still taking some type of classes—I think regarding mixed gasses, maybe with Rebreathers—at Tom’s house. In fact, I was one of Tom’s instructors who did the final proofreading of one of Kevin Gurr’s manuals. Too far back to recall much about this mixed gas stuff—remember my reputation for being a deep air diver.

Tom Mount and Gary Taylor mixing up some trimix in the garage.

Speaking of the people with whom you’ve dived, was the aim of The Forty Fathom Scubapros Club?

Before I invested in a sinkhole in the Ocala, Florida, area—which was locally referred to as Blue Sink or Zuber Sink, and is now referred to as 40 Fathom Grotto—several diving buddies whom I had dived with and trained for extreme deep air diving—as well as cave exploring—got together and planned to dive The Grotto at least one Friday night per month. Within a short period of time, several other buddies joined our group, which eventually became known as The 40 Fathom Scubapro’s dive club. Each diver had to meet my requirements of training. 

Forty Fathom Grotto aka Zuber Sink
An early Sheck Exley mix course at Forty Fathom Grotto
An Eric Hutcheson drawing of Forty Fathom Grotto

Eventually, our group set specific personal requirements—being a good person, supporting our club safety rules, and making at least one 40 Fathom Grotto dive per month. We set a limit of 14 or 15 members. Three 40 Fathom members eventually set World Records for deep air: I was one, A. J. Muns, and Herb Johnson set ocean records, and later I set the air depth record for cave diving. Naturally, as time passed and we got older, our membership got smaller. It is notable that none of our club members have died during any scuba dive.

Finally, what led you to create the iconic motto, “Plan Your Dive. Dive Your Plan?” 

I used to be a private pilot, and we used to say, “Plan your flight, fly your plan.” This was back in probably 1961 when I had just started diving and there were so many instances where all the other divers would get in the water without saying anything. I’ve seen so many incidents and fatalities that could have been avoided through proper planning.

Dive Deeper

ScubaGuru: LXD 029 : Hal Watts – Record Deep Diver & Technical Diving Pioneer

Netdoc: Netdoc chats with Mr Scuba, Hal Watts

InDEPTH: The First Helium-based Mix Dives Conducted by Pre-Tech Explorers (1967-1988) by Chris Werner

Alert Diver.Eu: Rapture of the Tech: Depth, Narcosis and Training Agencies

Professional Scuba Association International: PSAI History


Andrea Murdock Alpini is a TDI and PSAI technical trimix and advanced wreck-overhead instructor based in Italy. He is fascinated by deep wrecks, historical research, decompression studies, caves, filming, and writing. He holds a Master’s degree in Architecture and an MBA in Economics for The Arts. Andrea is also the founder of PHY Diving Equipment. His life revolves around teaching open circuit scuba diving, conducting expeditions, developing gear, and writing essays about his philosophy of wreck and cave diving. He published his first book, Deep Blue: storie di relitti e luoghi insoliti (2018) and IMMERSIONI SELVAGGE, the new one is on the way, out on fall 2022. 

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