A Look Inside Rebreather Scrubber Canisters, Part 1

If you’re diving a rebreather (closed-circuit breathing apparatus to be exact), then you know the scrubber removes carbon dioxide from your recirculated breath. Without the scrubber working, you’d go unconscious from carbon dioxide intoxication within a very few minutes of starting the dive.

But do you really know what’s going on inside that scrubber canister?

A stochastic computer simulation developed by the author gives as realistic a glimpse inside as we can get.

Loose granular and rolled sodalime. Click to enlarge.

Carbon dioxide scrubber canisters usually contain a chemical mixture called sodalime that chemically reacts with carbon dioxide in a diver’s expired breath. That material may be in granular form, or in a preformed roll. Sodalime is a mixture of calcium hydroxide and sodium hydroxide, which when it reacts by absorbing carbon dioxide is converted into calcium carbonate (CaCO3, calcite), a major constituent of limestone.

The overall chemical reaction can be simplified to:

CO2 + Ca(OH)2 → CaCO3 + H2O + heat

In the following sequence of images we see a rectangular prism shaped scrubber canister arranged axially such that the diver’s expired breath enters the section from the left, passing completely through the canister section before exiting to the right. A portion of the canister was cut away digitally after the simulation was run to allow visualization of temperatures within the canister interior.

Beginning of the simulation. Click to enlarge.

Initially, the canister is at room temperature, and then is immersed in cold water as the diver begins his dive. Temperature is color coded: the coldest temperature is black, and increasing warmth is portrayed in an intuitive fashion from purple to red to yellow, and finally white, being the highest temperature.

In the first image, CO2 has just started reacting with the sodalime at the entrance to the canister section, with a slight heating resulting. Thermal conduction is cooling the exterior surface of the canister, but most of the inside still remains at room temperature.

In the second image, the reaction front has clearly formed, and the hottest portion of the canister has begun moving downstream. Convection carries heat rapidly downstream to heat the diver’s inspired breath, and is seen to offset canister cooling due to conduction from the surrounding cold water.

Click to enlarge

In the image to the left, the heating front is fully developed, and residual heat has spread almost completely throughout the downstream portion of the canister.

In the next image, to the right, the front is beginning to weaken in intensity.

 

 

 

Finally (lower left figure), the thermal heating in the reaction front, indicative of CO2 absorption effectiveness, is fading out, and the cooling of the canister from the surrounding cold water is beginning to win the tug of war between heat generation and conductive cooling.

At that point in time, the canister is spent, and essentially all of the exhaled CO2 is passing right through the canister without being absorbed. If the diver had not ended his dive before his canister reached this point, he would be at great risk of passing out due to CO2 accumulation.

The last figure (lower right) shows temperature readings at various locations, and at various times (reps) throughout the simulation run. The orange and brown traces marked “temp” are measured temperatures from locations near the entrance to the canister. They rise abruptly as the absorption reactions start, and fall quickly as the reaction front moves past them, downstream.

Click to enlarge

The curves that remain elevated longer represent the average exhaled gas temperature, and the average temperature within the absorbent bed. After reaching a peak, the average bed temperature steadily drops as cold gas from the inlet (exhaled) gas chills the portion of the bed behind the reaction front. Exhaled gas temperature, on the other hand, climbs more slowly, but remains more stable until the bed becomes depleted of absorbent activity.

The monitoring of absorbent canister temperature changes is what makes the rebreather scrubber canister monitors used in the Inspiration and Sentinel rebreathers possible. The Sentinel technology is licensed from the U.S. Navy Experimental Diving Unit.

In the next posting, we’ll see the surprising way that cold canisters fill up with calcium carbonate.

 

 

 

 

 

 

 

 

 

The following is a high definition video of the computer simulation of heat generation and loss in a short cylindrical canister. For best effect go to full screen and 1080p mode.

 

 

Further details about the computer simulation involved in the production of these images and video can be found in the paper “Computer Modeling of the Kinetics of CO2 Absorption in Rebreather Scrubber Canisters”, in MTS/IEEE OCEANS 2001 Conference Proceedings, published by the Marine Technology Society; Institute of Electrical and Electronics Engineers; Oceanic Engineering Society (U.S.); IEEE Xplore (Online service).

Diving Accident Investigation

Diving helmets waiting for accident investigations. Click for a larger image.

Compared to aircraft accident investigations, diving accident investigations are often ad hoc in nature, poorly conceived and poorly funded. Nevertheless, these investigations are just as important for the safety of the diving public as are similar investigations for the flying public. Unfortunately, no national regulations presently address how investigations of diving accidents should be conducted: volunteer investigators have no legal status for extracting information about an accident, and they have no legally binding protection from litigation based on the conduct of their investigation or on its results. That is, no business case can be made for conducting diving accident investigations, in spite of the moral authority for conducting them.

With the conviction that this untenable situation must eventually change, this presentation will describe one approach to diving accident investigations with particular emphasis on rebreathers and will draw some comparisons to aviation accident investigations by the National Transportation Safety Board (NTSB).

Aircraft accident investigations

The "black box" containing data recorded just prior to, and during, a commercial aircraft accident.

Pilots know that if they are involved in a fatal crash, the NTSB will investigate the accident by examining in excruciating detail everything those pilots did for hours, perhaps even days or weeks, leading up to that accident. It will investigate how often they called flight service to check on the weather. The NTSB will go through those pilots’ personal logbooks to check on their currency and proficiency, and it will check Federal Aviation Administration (FAA) records for a history of violations. NTSB investigators will also examine an aircraft’s logbooks to scrutinize its maintenance records. They will play back voice and radar data, and if a data recorder is available, they will analyze its contents.

Then they get personal. The NTSB and its FAA counterparts will talk to mechanics, surviving passengers, and friends to ask questions such as, “What were the aviators’ attitudes toward flying? Were they cavalier? Did they take unnecessary risks, or were they careful and methodical?”

Accidents happen.

Due to the detailed, scripted nature of NTSB procedures, the investigation may take up to a year to complete.

A few years ago a pilot’s engine failed and he was forced to make a water landing just off a beach. The ditching should have been survivable, but he lost consciousness on impact and sank with the airplane as it settled to the bottom in relatively shallow water. He drowned.

If he had been a diver, that would have been the end of the story. The public judgment would have been, “A diver drowned. He tried to breathe underwater; this is what happens.” But this victim happened to drown inside an airplane. So instead of the medical examiner simply saying that he drowned, the NTSB started its very thorough investigation procedures.

Fortunately, the pilot also had a surviving passenger. From the survivor’s statement, the aircraft’s maintenance records, and the mechanic’s testimony, an ugly story of reckless disregard for the most basic safety rules of flying began to emerge.

Do divers ever show a reckless disregard for basic safety rules? You bet. It’s unfortunate that the pilot died, but the events leading to his death were a useful reminder that the media in which we work and play, high-altitude air and water, are not forgiving. Humans are not designed for flying or diving, and nature only begrudgingly lets us trespass — on its terms.

The U.S. Navy and Coast Guard are chartered to investigate diving accidents. Unfortunately, there is a huge discrepancy in the number of personnel and the amount of funding for aviation accident investigations compared to diving accident investigations. The NTSB has hundreds of personnel and tens of millions in funding available, whereas the entire U.S. Navy has at most a handful of investigators with no investigation-specific funding.

Investigation team requirements

In the best of all worlds, an investigation team should have access to both a manned and an unmanned test facility, access to experts in all diving equipment (scuba, rebreathers, helmets), and the ability to conduct and interpret gas analyses — sometimes from minuscule amounts of remaining gas. At a minimum, such a team needs the ability to download and interpret dive computer/recorder data. Some investigations may require the simulation of UBA-human interactions for “re-enactment” purposes. An investigation team should also have diving medical expertise available to review medical examiner reports for consistency with known or discovered facts regarding the accident. Last, it should have in-depth knowledge of police investigative procedures, particularly of the procedures and documentation for maintaining “chain of custody”.

Do rebreather investigations have a future?

Considering the resources and time-frames required for laboratories such as the Navy Experimental Diving Unit (NEDU) to conduct diving equipment evaluations on a limited set of accident cases, and the unfunded costs associated with those investigations, it is difficult to imagine a resolution to an ever-increasing need for rebreather investigations. Almost certainly, no independent federal agency similar to the NTSB will ever be responsible for investigating diving accidents, simply because diving accidents lack national attention: the public at large is not being placed in jeopardy.

It is also unlikely that diving equipment manufacturers would welcome federal agency oversight and regulations comparable to those engendered by the FAA and NTSB. Diving might become exorbitantly expensive. For instance, if a $5 part available for purchase in an automotive store were to be used in an aircraft, it would become a $50–$500 part because of FAA required  documentation that it meets airworthiness standards.

The U.S. Coast Guard initiates diving accident investigations and in some cases conducts hearings into those accidents; however, with its enhanced role in Homeland Security, the Coast Guard is unlikely to welcome any efforts to diversify its mission. The cost/benefit ratio would appear to be too great.

For the future, as Dick Vann of DAN has suggested, the resolution may ultimately depend on rebreather users funding a team of dedicated, professional accident investigators. The cost of conducting worthwhile investigations has yet to be determined, and therefore the amount of funding needed to support it is unknown. I suggest that obtaining those estimates should be a priority as we, rebreather users and the industry, decide the next steps in investigating rebreather accidents.

 

The above are highlights from this author’s publication of the same name, found in: Vann RD, Mitchell SJ, Denoble PJ, Anthony TG, eds. Technical Diving Conference, Proceedings. Durham, NC: Divers Alert Network; 2009; 394 pages. ISBN# 978-1-930536-53-1.

This book is available for download at no cost as a PDF file from the Divers Alert Network website (http://www.DiversAlertNetwork.org/or from http://archive.rubicon-foundation.org/8300

Divers In Space

Signs of flowing water have been found on Mars. http://www.nytimes.com/2011/08/05/science/space/05mars.html?_r=1

That of course makes Mars even more tantalizing than it is already.

Now Mars has been added to a growing list of bodies in our solar system that are believed to have water, and in some cases entire oceans. Let me be so bold as to pronounce, where you have water, you will eventually need divers.

Biosphere 2

I once attended a joint NASA – Diving Conference at Disney World in Orlando. It was largely devoted to discussions of the science and engineering that would be required to send men and women to Mars and to sustain them in a colony. I was presenting a diving related talk at the invitation of one of the editors of the Life Support & Biosphere Science journal, a short-lived scientific journal that reported on the science conducted in Biospheres and other life-support systems.

After hearing a number of fascinating NASA accounts, I talked about a rather arcane subject: A Priori models in the testing of diving life support equipment. That work was published in 1996. At the end of the talk, a NASA engineer asked, somewhat smugly I felt, how diving had anything to do with space.

Well, that wasn’t at all the purpose of the meeting, or the reason why I was talking. The organizers believed, correctly, that sojurns in space and underwater share elements in common; namely, people and breathing equipment. We could, and should, learn from each other.

Now, regarding the question: I can ad lib with the best of them. Knowing that Jupiter’s moon Europa was believed to be hiding a large ocean beneath its icy surface, I responded that someday astronauts will be carrying a dreadfully expensive piece of hardware to an alien moon or planet with water, and that priceless tool will get dropped  — into the water. It happens all the time on Earth.

Now what? You can’t go on-line, order a replacement, and expect an overnight FedEx shipment.  That is when a space diver would be worth his Earth-weight in rhodium.

Saturn's moon Enceladus

Since that time, we’ve learned that Saturn’s moon Enceladus jets water from its south pole.  As reported in the journal Icarus, that suggests that, like Europa, there may be a liquid ocean beneath the moon’s icy crust.

My suspicion is that long before we’ll need cowboys in space, we’ll need divers in space.

So divers, keep your diving helmets oxygen clean. You may get the call any day now.

How to Teach Ice Diving When the Arctic Is Melting

In 2007 Michael Lang of the Smithsonian Institution’s Scientific Diving Program sponsored a spring-time ice diving course in the high Arctic at Ny-Ålesund, Svalbard, in an area generally called Spitzbergen.

Ny-Ålesund, an international Arctic research town situated at 78°56’N, 11°56’E, is the most northern continuously operated community. It sits on the shore of a fjord called Kongsfjorden. In the springtime, the sea ice on the Kongsfjorden is usually several feet thick, providing an inviting platform for ice-diving operations.

North Pole Hotel, Ny-Ålesund, Svalbard

However, during the last decade the sea ice has been becoming thinner and sparser. By the time we arrived, there was virtually no ice on the fjord. The closest ice source was a glacier over two miles away. With no ice, polar bears could not capture their ringed seal prey, and were thus hungry, leading undoubtedly to the polar bear encounter described in an earlier posting (April 12).

It also left the course instructors, and I was once of them, in a quandary. It was expensive transporting diving scientists to the high Arctic to learn ice diving operations, and there was no ice to be seen. It appeared to us that the Arctic really was melting, surprisingly early in this case.

Although we had a few frigid days during our week-long stay, frigid enough to remind us we were close to the North Pole, one memorable day was almost balmy, reaching 0° C (32° F). Looking out over the fjord I saw mini-icebergs, recently calved by the rapidly melting glacier a few miles away.

Mini-icebergs, born on an unusually warm day

The word went out to launch all divers.

Dry land and underwater cameras, and high-definition video were working overtime to record the encounters between divers and ice. The result was some striking photos of delicately scalloped floating ice, with divers getting into the frames — just to prove they were indeed “ice-divers.” Unfortunately, that was not the type of experience that had been planned for those scientists.

Transparent glacial ice

As you might imagine, the water in the fjord was still bitterly cold, so the part of the course designed to teach about human and equipment survival in cold water was fully accomplished.

However, due to the growing sparseness and unreliability of the Arctic sea ice cover, the Smithsonian Diving Program has now moved its training and testing operations to McMurdo Station, Antarctica (see April 11 and May 26th posting). There, at least for the time being, lies plenty of thick sea ice covering the Ross Sea during the austral springtime.

I had not been impressed by the global warming rhetoric before I traveled to the Arctic. However, having seen the consequences first hand, at least in the far North, I get the strong impression that there are undeniable local climate changes occurring. Whether it is a truly global change, and whether man is somehow responsible, is an area of speculation that I will not venture into.

Only time will tell.

Why Deep Saturation Diving Is Like Going to the Moon, and Beyond

This week, as the Space Shuttle is making its last circuits around our planet, I lament what has happened to our space program. Yet, I am reminded of another exploration program that has, like the shuttle and the moon programs, reached incredible milestones only to retreat to a less exotic but still impressive status. That other program is experimental, deep saturation diving.

I have been privileged to conduct human physiological research on several deep saturation dives, one being a record-breaking U.S. Navy dive at the Navy Experimental Diving Unit (NEDU) in 1977 to a pressure equivalent to that found at 1500 feet sea water (fsw), or 460 msw*, and on a 450 msw (1470 fsw) dive at the GUSI diving facility at the GKSS Institute in Geesthacht, Germany in 1990. For perspective, the safe SCUBA diving depth is considered to be 130 fsw, although technical and cave divers often descend deeper, to 300 fsw or so.

NEDU, Panama City, FL

Dives in hyperbaric chambers like at GUSI and NEDU are simulated; the divers don’t actually go anywhere. But the effects of the high pressure on the divers’ bodies are just as they would be in the ocean. Of course, even in simulated dives, divers wear Underwater Breathing Apparatus, and descend into water contained within the hyperbaric complex.

In 1979, NEDU again set the U.S. Navy record for deep diving to 1800 fsw (551 msw). At Duke University in 1981, the U.S. record for pressure exposure was set by three saturation divers inside an eight-foot diameter sphere. The internal pressure was 2250 fsw (686 msw). One of those divers went on to become the senior medical officer at NEDU, none the worse for his high pressure exposure.

The French company Comex, of Marseille used an experimental gas mixture of hydrogen-helium-oxygen to reach 675 msw, before being forced back to 650 msw due to physical and physiological problems with the divers. However, like teams attempting the summit of Mount Everest, one diver from the dive team was pressed to a world record of 701 msw (2290 fsw), just squeaking past the U.S. record.

There is a poorly understood physiological barrier called the High Pressure Nervous Syndrome (HPNS) that limits our penetration to ever deeper depths. In spite of the use of increasingly exotic gas mixtures, helium-oxygen in the U.S. Navy, helium-nitrogen-oxygen at Duke University, and hydrogen-helium-oxygen at Comex, all attempts to dive deeper have, to date, been rebuffed.

Just as I had thought as a young man that trips to the moon would be common-place by now, I had also assumed diving to 3000 feet would be routine. But it is not.

In my early research days I was interested in the effects on organisms of very high pressure, 5000 psi, which is equivalent to a depth of over 11,000 feet (3430 meters). We now know those effects can be profound, altering the very structure of cell membranes. Reversing those effects while maintaining high pressure, at great depth, is a daunting scientific task. We don’t yet know how to do it.

What we do know is that reaching 1500 feet can be done without too much difficulty. In the 1980s it became almost routine to dive to 1000 feet at both the Naval Medical Research Institute (Bethesda) and NEDU. Deep saturation diving is a thriving business in the oil fields of the Gulf of Mexico and the North Sea.

Click for a larger image.

But as for the similarity between deep saturation diving and NASA’s moon missions, in the Apollo program it took slightly over three days to get to the moon, and almost an equal time to return. But as the above dive profile shows, it took sixteen days to reach the maximum depth of 1500 fsw, and seventeen days to safely return. Over that period of time astronauts would have whizzed past the moon and been well on their way to Mars. Unlike spacecraft and astronauts, divers must slow their descent to avoid HPNS, and must slow their return to the surface to avoid debilitating and painful decompression sickness. Diving without submarines or armored suits is very much a demanding, physical stress.

Politically, exceeding our current depth limits of approximately 2000 feet is akin to returning to the moon, and going beyond. We could do it, but at what cost? Should we? Will it ever be a national priority?

Maybe not for the United States, but I have a suspicion that other countries, perhaps not as heavily committed to space as we, will find the allure of beating current diving records irresistible. If there are medical or pharmacological interventions developed for getting divers safely and productively down to 3000 feet, then that would be a scientific achievement comparable to sending men to Mars.

*[The feet to meters conversion is slightly different from the feet of sea water to meters of sea water conversion. The latter represents pressure, not depth, and therefore includes a correction factor for the density of sea water.]

Outsmarted by an Octopus

Jim Duran and I started a night dive in about sixty to seventy feet of water several miles off the beaches of Panama City, FL. I was wearing double 80 tanks, held a collecting bag and lights, and fully intended to capture an octopus, alive.

At the time I was working in an invertebrate physiology laboratory at Florida State University, under the mentorship of Dr. Michael Greenberg. I had been impressed by the reputed high intelligence of the octopus, and was also interested in the effects of high pressure. The Navy base at Panama City had a new high pressure chamber, capable of simulating deep-sea pressures. Since I was in training in the combined Navy and NOAA program called the Scientist in the Sea, it seemed logical to me to catch an octopus, and study it to see if it would be a suitable candidate for testing in the Navy’s  giant hyperbaric chamber.

It sounded like a reasonable plan to me, and Jim Duran was willing to follow along as my assistant critter catcher. And to begin with, the plan worked. We spied our quarry only a few minutes into the dive. The gray-brown octopus was crawling over the sandy bottom, and initially seemed unaware of our intentions. But as the two of us closed in on him, specimen bag flapping in our self-generated current, he sprang off the bottom and squirted away.

But we were strong swimmers, and our quarry was in the open, maybe eight feet off the bottom. He had nowhere to hide – silly thing. Keeping our lights on him, and stroking like mad, I began gaining on him, at which time he let loose with his ink. I was prepared for that, and continuing to kick I soon caught up with him and got my hands on him, trying to stuff him into my bag. But he would have none of that.

Off we went again. What we didn’t realize was that the clever invertebrate was constantly turning to our right. We of course were too intent on capturing him to notice his strategy. And besides, invertebrates were incapable of strategic planning – or so we thought.

Apparently the octopus was determined not to be touched again, or else we were tiring, for we never quite caught up with him. So close, and yet so far away.

And then a curious thing happened. He collapsed his tentacles upon themselves, streamlining his body shape, and shot like a rocket from our depth to the sandy bottom. Once on firm ground again, he spread his tentacles as wide as he could, and his entire body turned white. I froze in shock.

In another instant, before I could recover my senses, he collapsed his body down to the width of an apple and slithered into his hole in the sea floor.

He was gone.

It didn’t take long for us to realize that the chase had started near his home, and he had led us at a furious pace in a large circle, which ended precisely where it had begun. He had maneuvered us to within striking distance of safety.

Humbled, and now growing low on air, and embarrassingly empty-handed, we headed back to the off-shore platform where our dive had begun.

It had seemed like such a good idea. Who knew that two graduate students would be outsmarted by an invertebrate.

Below is a link to a video showing an octopus’ ability to disguise itself, and some of the defensive behavior we witnessed.

[youtube id=”PmDTtkZlMwM” w=”500″ h=”400″]

Liquid Breathing – It’s Not As Easy as It Looks

Who can forget James Cameron’s movie The Abyss!

If I need to remind you, Cameron is the creator of Avatar.

The Abyss was an imaginative movie of the 1980s, where the plot concerned commercial divers who had been hired by the Navy to assist with the salvage of a nuclear submarine. It involved very deep diving, and special technology that actually has some basis in fact.

By far the most memorable part of the movie involves a diving helmet filled with a liquid that the diver, with some trepidation, breathed.

Below is a clip from the movie that demonstrated, quite dramatically, and with a live animal, the concept of liquid breathing.

It’s not a trick – it really works, on small rodents.

In the 1960s and 70s the Office of Navy Research funded basic research at Duke University on liquid breathing, with Dr. Johannes A. Kylstra as the lead scientist on the project. After proving the technique worked on rodents and dogs, it progressed to the point of having a commercial diver, Frank Falejczyk, become the first person to breathe oxygenated liquid.

First, Frank inhaled well-oxygenated saline on an operating table. Unfortunately, extraction of the liquid from his lung did not work as planned. He developed pneumonia as a result of the exposure. But eventually, the researchers found that oxygenated perfluorocarbons could be tolerated by the lung, and could, at least in animals, allow the extraction of dissolved oxygen for a period of time without ill effects.

Eventually, Falejczyk made a presentation on his trials to an audience that happened to include James Cameron.  Apparently, Cameron was impressed.

So, can man breathe liquid and not drown? At least one retired physician says yes. Arnold Lande, a retired American heart and lung surgeon, has patented a scuba suit that would, he suggests, allow a human to breathe oxygenated liquid.

http://www.independent.co.uk/news/science/into-the-abyss-the-diving-suit-that-turns-men-into-fish-2139167.html

Now, making such a device work is in fact a tall order. Although Kylstra’s animal experiments showed that rodents and even dogs could be ventilated for up to an hour, the limiting factor seemed to be the accumulation of carbon dioxide in the body. The perfluorocarbons gave up their stored oxygen readily, but did not adequately eliminate carbon dioxide.

That is a major problem.

In the 1980s an Israeli colleague and I conducted biomedical research on potential Navy applications of high frequency ventilation (HFV), an unusual method of mechanical ventilation that now has many clinical applications. It soon occurred to me that appropriate frequencies applied to the mouth or chest wall could greatly accelerate the diffusion of carbon dioxide in liquid, just as it did in air. However, I never proposed studying liquid ventilation, and if I had, the proposal would likely have been rejected almost immediately on the basis of Frank Falejczyk’s bad outcome.

Dr. Lande has proposed solving the carbon dioxide retention problem by tieing artificial gills straight into the human circulatory system. There are obvious safety concerns with such a plan, but if those concerns could be engineered out, there is still the problem of creating working gills with enough throughput to eliminate CO2 from a working diver.

I once witnessed a demonstration of an artificial gill, conducted in front of several well-educated Navy diving physicians and scientists. After descending about three feet down into a pool, the “inventor” lay motionless for 30 seconds, then bounded up out of the water, breathlessly saying, “Basically, it works.”

His panted words were not convincing.

Based on fairly recent history, and the fact that for deep diving, not one lung but both lungs would have to be completely filled with perfluorocarbon or similar liquid, it seems that a practical and safe liquid breathing system will be a huge engineering challenge. I can envision ways that it could be done, but at what cost, and for what purpose?

I am mindful, being an aviator, that such questions were not allowed to stymie Wilbur and Orville Wright. However, these days, human experimentation involving the complete filling of human lungs would face a formidable hurdle, called the Human Use Committee.  In the U.S. at least, a repeat of Kylstra’s experiments is very unlikely to be approved by Research Ethics committees.

But could it happen in other countries with lessor human research safeguards?

Time will tell.

My Top Three Diving Sites: Herod’s Port, Caesarea

Visibility was lousy that day, which made the dive just that much more exciting.

I and some U.S. Navy SEALS were cruising in shallow water searching for antiquities, when out of the gloom appeared, fuzzy at first, and then with startling clarity, a fluted Roman column lying on its side. The effect was stunning.

We were diving in Caesarea, the location of one of the finest Mediterranean ports ever built before and during the time of Christ – designed to compete with the contemporaneous port in Alexandria, Egypt.

Two SEALS, two diving scientists, and a physician.

As we swam on, we encountered large frames made of hydraulic concrete, with remnants of wood still embedded within them. I could barely believe what I was seeing! The Romans had concrete, and used it underwater?

Well, there it was. And imbedded within the concrete remained some of the original wood used within the frames.

I’ve since learned that Roman engineers used a type of hydraulic cement called pozzolana. According to a local maritime historian,

“The Romans found that when they took the volcanic powder found around Mount Vesuvius and mixed it with lime and rubble, the substance hardened in water.” … “This ‘hydraulic concrete’ was imported to Casearea and used to fill wooden frames which were then lowered into the water to lay the foundations for the port.”

At the time of our visit, the diving site was not yet open to tourists, but now it is the site of an underwater museum, through a concerted effort of archeologists and historians.

Which worries me a little. You see, on that dive I didn’t have as much weight on my weight belt as I should have, so I picked up a stone and carried it around with me throughout the dive. Of course as I surfaced from the shallow dive I left the rock on the bottom, somewhere. If that stone had some archeological significance, the information about its placement, relative to the rest of the sunken port, was destroyed by my use of it.

I can only hope that it was a ballast stone from one of the many merchant vessels visiting that port two thousand years ago. That it should serve as my personal ballast stone feels fitting somehow. It was perhaps a connection tying me to ancient mariners.

Or else, it was just conveniently located junk. But, I can imagine, can’t I?

As of 2006, Herod’s Port has been accessible to tourist divers as an Underwater Museum. Now anyone can dive there, with the benefit of waterproof underwater maps and well marked archeological artifacts.

Caesarea is not your usual diving location, but it is important enough, historically, to make it into my top three.

My Top Three Diving Sites: The Red Sea Pt. 2

I was one little inch away from BIG trouble.

Twenty kilometers north of Sharm el-Sheik are four current-swept reefs that attract Red Sea divers and bountiful sea-life alike. We left for the dive site from Ras Nasrani, heading for Thomas Reef, in the middle of the current-swept Straits of Tiran.

Thomas Reef is the smallest but most popular reef for diving. Because of the current, it requires a different diving technique than the simple but awe-inspiring wall dives at Ras Mohammed. Our dive boat with some diving professionals and tourists onboard anchored just off  Thomas Reef  and quickly had its bow swept into the current.

The plan was to enter the water from the stern, and follow the anchor line down to a point where we could kick like mad and make our way to coral encrusted rocks. From there, it would be a fairly short swim against the current, using the rocks for assistance, until we entered the calm water in the lee of the reef.

Thomas Reef provides a unique dive site due to the sea life attracted to the current. Because of that, it is well worth negotiating the heavy flow; rewards awaited the determined diver. In my case, a surprise awaited me as well.

As I let loose of the anchor chain, I could clearly see the steeply sloping bottom features of the reef, where I was headed. I spotted my target rock and kicked mightily until it was in my grasp. Now anchored, I had time to survey the beauty around me, and plan my next step. It was then that I noticed that an inch way from my naked right hand, the one firmly grasping the rock, sat not just another stone, but a stone with eyes.

It was in fact, something far more dangerous than a stone —  it was a stonefish.

Red Sea Stonefish

Stonefish are reputed to be the most venomous fish in the world. Had I grabbed it instead of its stony neighbor, glands at the base of its many dorsal spines would have flooded my bare hand with venom. The sting causes intense pain; with the affected body part swelling rapidly, potentially leading to death of tissues.

Just how bad the symptoms become depends on the anatomical location of the punctures, depth of penetration and the number of spines involved. The effects of the venom are muscle weakness, temporary paralysis and shock, which, if encountered during a scuba dive in a strong current, could make a safe return to the dive boat somewhat  difficult. If not treated, the incident could prove fatal.

The emergency treatment required is  much more than is likely to have been available on a chartered dive boat. As breathtaking as a Red Seas trip promises to be, you might stumble across critters that can take your breath away, literally. So a check of the closest and most capable medical facility should be high on your pre-dive checklist.

No doubt about it, if I had grabbed the wrong “stone” I would have been in a world of hurt; and probably in a lot of trouble with my dive buddies as well since that trip would have been brought to a sudden and exciting conclusion.

Oh yeah, once I overcame my surprise, and moved on, ever so carefully to the lee of the island-like reef, the experience was everything I had come to expect from the Red Sea.

Highly recommended!

My Top Three Diving Sites: The Red Sea, Sharm el-Sheik

I’ve read a couple of books lately where the author, critically injured in an accident, experiences what seems to be a visit to heaven, followed by a swift return to Earth.  The most recent such book was Flight to Heaven, by CAPT Dale Black, a plane crash survivor.

A common theme in these books is that the author finds colors in Heaven to be much purer and vibrant than any colors seen on Earth. Well, I know a place just like that, and for a diver it must indeed be heaven on Earth. It’s called the Red Sea.

Sharm el-Sheik and Ras Muhammad are located on the southern tip of the Sinai Peninsula, where the Gulf of Suez and the Gulf of Aqaba meet the Red Sea. On my first dive at Ras Mohammed, as I sank below the water’s surface I saw a wall of color that defied description. The phrase, “a riot of color”, is a cliché, but that is what I saw. It was as if every inch of the reef was shouting for attention, clamoring to be the most colorful, the most interesting piece of rock ever created. I was stunned — in sensory overload from the beginning to the end of that dive.

At Ras Muhammad, the coral encrusted wall dropped at a dizzying angle, headed for depths of 3000 feet, 1000 m, a very short distance from shore. I had planned a dive to no more than sixty feet, where the natural light was bright enough to show off the colors cascading downward, towards what seemed to be a bottomless abyss. But at sixty feet I saw a never ending waterfall of fauna, just a few feet below me, and then below that, even more. The colors were still spectacular even at that depth, defying all the laws of physics as I understood them.

When I realized I was twenty feet below my planned dive depth, a curious thing happened. I stopped searching for the next most beautiful thing, stopped my descent, but for a few moments I had an almost overwhelming desire to throw rational thought aside and continue down into the abyss.

I understood the consequences of that action, had I continued deeper, but the experience in that moment seemed to transcend my worth as a human being. The living communal organism, and all the life forms sustained by it, clutching close to the wall, seemed to have much greater significance in the whole scheme of things than I did. I felt a kinship, perhaps pointing to our theorized evolutionary beginnings, that made it seem that where I was, was where I belonged.

Napolean Wrasse - Egypt. (Photo credit - Sami Salmenkivi.)