Archive for the ‘Scuba Diving’ Category

Freediving in Ireland

Taking the oxygen-free plunge

Lifeguards at public swimming pools don’t like it when you disregard the signs that say “Walk, Don’t Run!” But they like it even less when you don’t move at all. As a lifeguard is scanning the pool, the last thing they want to see is a body floating face-down and motionless in the water. I remember getting yelled at for doing exactly that when I was about 10 or 12 years old. I couldn’t understand what the problem was. I wasn’t bothering anyone, I was just enjoying the sensation of holding my breath, floating, and staring at the bottom of the pool. But the lifeguard reprimanded me: “You have to keep moving! Otherwise I won’t know if you have drowned.” I thought that was unfair, because kicking around in the water isn’t as relaxing or serene as just floating there, but ever since then, as a courtesy to those who could not discern my state of consciousness from a distance, I have refrained from floating face-down.

Little did I realize that what I was doing would soon be a major competitive sport.

Kicking the Breathing Habit

Serious breath-holders would call what I was doing Static Apnea—just one of several categories of the sport of freediving. The current world record for Static Apnea is held by Serbian diver Branko Petrović, who floated in a swimming pool while holding his breath for eleven minutes and fifty-four seconds. That is, if I may say so (and pardon the pun), an unfathomably long time. But it’s just the tip of the iceberg. Freediving is all about pushing the limits of physical and mental endurance, defying common sense all the way.

Freediving is the name for a class of activities that involve holding one’s breath underwater for an extended period of time. In its simplest form, freediving is a low-tech alternative to recreational scuba diving. Although freedivers can’t stay submerged as long as divers who use tanks and regulators, they can move much more quickly and freely without the drag caused by the equipment. It’s a quieter experience too, and with fewer bubbles there’s less chance of scaring off fish. The only equipment required is a mask, wetsuit, and extra-long fins, making it a less expensive pastime than scuba diving as well.

The Length and the Breath

But when you start talking about competitive freediving, it begins to sound like a sport that could only be appreciated by someone whose brain had been deprived of oxygen a bit too long. Static Apnea is all well and good, but serious freedivers consider that just the first step. Dynamic Apnea ups the ante by requiring the diver to swim horizontally underwater; the idea is to cover as much distance as possible without taking a breath. Separate categories exist for divers using fins and those without. But then things start getting really interesting. In the other major forms of freediving, a rope (with markings to indicate depth) is dropped to the sea floor, and the objective is to follow the rope as deep as possible before returning to the surface. In a Constant Ballast dive, divers must descend and ascend under their own power; they can optionally use a weight to help them descend but they must carry the same weight on the way back up. Free Immersion is similar, except that the diver can pull on the rope to assist in the descent and ascent. Then there’s the Variable Ballast dive, in which a weighted sled takes the diver farther down into the water; the diver then leaves the sled to ascend under his or her own power. If that’s not challenging enough, a No Limits dive uses the same weighted sled to go even deeper, at which point the diver inflates a lift bag to facilitate a speedy ascent.

Austrian diver Herbert Nitsch currently holds the world record for No Limits free diving, generally considered the most challenging category. On June 14, 2007, he made a record No Limits dive of 214m (702 feet). But freediving is intensely competitive, and records are set and broken with astonishing frequency. The endless push to go deeper and longer is, not surprisingly, very risky, even for extremely well-trained divers. In October 2002, world-renowned freediver Audry Mestre died in an attempt to break the record at the time with a dive of 170 meters. A combination of equipment malfunction and human error prevented her from ascending fast enough, despite the numerous safety measures that are always taken during dives of this sort. Similarly, in November 2013, Nicholas Mevoli from New York died in an attempt to break the Constant Ballast Without Fins record. But these tragedies seem to have had a galvanizing effect on the freediving community, inspiring them to push themselves even further as a tribute to their lost comrades.

If you think about other mammals that hold their breath to make extended dives—whales, seals, and sea lions—freediving doesn’t sound all that crazy. Human physiology is quite a bit different, but research has shown that with training, almost anyone can develop the ability to hold their breath for three or four minutes. Still, there’s a big difference between holding your breath on the surface of a nice, safe swimming pool and doing the same thing under hundreds of meters of water. That requires stamina, guts, and probably a little insanity.

Note: This is an updated version of an article that originally appeared on Interesting Thing of the Day on July 30, 2003, and again in a slightly revised form on March 22, 2005.

Image credit: Simukas771 [CC BY-SA 4.0], via Wikimedia Commons

Source: Interesting Thing of the Day

Diver using a rebreather

Taking scuba to new depths

If I end up completing all the tasks on my Life’s To Do List, I’ll live to be a very old man indeed. So many places to visit, books to read, foods to try, experiences to have—and the list is perpetually growing. “Learn scuba diving” is on the list, but like “visit Machu Picchu” or “have sushi at Sukiyabashi Jiro,” it’s something that requires a greater investment of time and money than I am able to make at the moment. Still, it’s something I’d like to do if the opportunity ever presents itself. Yes, there’s a lot of fascinating stuff underwater—the marine life, the shipwrecks, and all—but equally appealing is the geek factor. Scuba diving requires lots of cool, specialized equipment, and just think of the entirely new range of dive-enhancing gadgets I could justify buying!

Then perhaps one day, if I become sufficiently advanced and still have some money to spare, I’ll invest in the ultimate piece of scuba gear: a rebreather. This fabulous piece of kit could set me back as much as US$20,000, not to mention the extensive additional training and certification I’d need to use it. But a rebreather does for scuba diving something like what a hybrid engine does for a car: it provides much greater fuel efficiency while reducing noise and pollution. These things may not seem like a big deal on the road, but underwater, they can make all the difference in the world. (Rebreathers are also used in spacesuits and gear for mountaineering and firefighting, among other applications, but I’ll focus on the underwater use here.)

Heavy Breathing

In ordinary scuba diving, you have one or more tanks of air—or, depending on what sort of dive you’re undertaking, a mixture of oxygen with nitrogen, helium, or other gases in carefully measured proportions. Regulators deliver just the quantity of air you need, at an appropriate pressure, through a mouthpiece; when you exhale, a valve releases the used air into the water. Each time you take a breath, though, your lungs absorb only about a quarter of the oxygen in the air; the rest is exhaled along with the carbon dioxide you produce. So a lot of the oxygen divers take with them is essentially wasted. The deeper you dive, the more rapidly you use up air, so a dive’s maximum duration is determined by its depth and the number of tanks a diver carries. Even though air tanks don’t feel heavy underwater, there are practical limits to how much a diver can carry, and thus limits on the duration of a dive.

Rebreathers change this equation by recirculating the unused oxygen from every exhaled breath. Instead of being expelled into the water, the used air is channeled into a “scrubber,” an assembly that uses a chemical such as a soda-lime mixture (sodium hydroxide and calcium hydroxide) to absorb the carbon dioxide. That leaves a good bit of usable oxygen, which is recirculated into the system and supplemented, as needed, with more oxygen from a tank. In this way, a rebreather can provide dramatically longer dive times with a much smaller and less cumbersome apparatus. In addition, because air isn’t discharged into the water when you exhale, there are no bubbles (or at least very few). As a result, a diver wearing a rebreather can swim almost silently and invisibly—handy if you’re photographing bashful fish or, you know, sneaking up on the enemy spy who’s trying to sabotage your submarine.

In the Loop

Conventional scuba apparatus is “open-loop” (or “open-circuit”), meaning the air goes out of the system when it’s been used. Most rebreathers, by contrast, fall into one of three major categories:

  • Oxygen rebreathers are the simplest variety. They use a single tank of pure oxygen, but because of the danger of oxygen toxicity (a situation where pressure forces too much oxygen into the blood), they can be used only at shallow depths of about 6 meters (20 feet) or less.
  • Semi-closed circuit rebreathers replace the oxygen tank with a tank of mixed gases, allowing deeper dives. But their design also requires that a portion of the used air be vented into the water to maintain the proper levels of oxygen and other gases.
  • Closed-circuit rebreathers are the most complex design. They use two gas tanks: one for air (or at least an oxygen-nitrogen or oxygen-helium mixture) and one for pure oxygen. Oxygen sensors feed data to a microprocessor that regulates the oxygen pressure in such a way that no gas needs to be expelled. Closed-circuit rebreathers also enable the diver to maintain very low levels of nitrogen (or other non-oxygen gases) in the blood, which reduces the need for slow decompression when ascending from deep water.

As great as rebreathers are for certain applications, they have some disadvantages compared to conventional scuba gear. For one thing, because rebreathers are so complex, more things can (and do) go wrong. They must be carefully maintained—and even then, they are far more prone to failure than a simple tank-and-regulator setup. (Failure of one’s breathing apparatus deep underwater, of course, is a rather serious problem.) In addition, it’s surprisingly difficult to regulate oxygen pressure precisely so that it falls into the narrow range between too little (which can result in a potentially deadly condition known as hypoxia) and too much (which can result in the potentially deadly condition of oxygen toxicity). If a rebreather fails to deliver just the right mix of gases, the diver is in trouble.

And of course there’s the price, which is not a big deal for the military, but problematic for many recreational divers. Note to self: Put “become fabulously wealthy” higher on Life’s To Do List than “learn to use a rebreather.”

Note: This is an updated version of an article that originally appeared on Interesting Thing of the Day on February 17, 2005.

Image credit: Peter Southwood [CC BY-SA 3.0], via Wikimedia Commons

Source: Interesting Thing of the Day

Firstly let me start by saying I came relatively late to the sport by most people’s standards at 37 but let me explain why it took so long.

I was always one of those people on holiday when they came round the pool or I was walking down the strip and they tried to get you to sign up for the PADI dive experience I would really fancy it but a quick glance to my partner and I would realise taking a couple of days out of our only 7 day break together to go diving would not end well for me. So I’d pass and say maybe next time.

Fast forward on repeat for 10 years & a couple of people at work were joining a local group but it seemed to be really haphazard lessons and they seemed to be in the pool forever, in fact in the time I worked with them I never actually heard either of them say they had actually been diving. This again put me off joining them as it all seemed very expensive in my head thousands of pounds on equipment & lessons to just swim in a pool.

On rolled another 5 years or so and a BSAC group were doing try dives for £10 in my gym on a Saturday morning, so this time I though why the hell not, what’s a tenner and I’m here on a Saturday anyway.

10968204_884675608222154_1829451416705410251_nSo I roll up on the day along with 3/4 other people and get my briefing, all good so far, we’re then given some kit to put on, 1st problem ….. I’m a big guy with size 13 feet, so squishing into size 10 fins is not comfortable but power through I do.

Once in the water a few lengths of snorkelling, something I’ve never been good at as I tend to look down too much and flood the snorkel, but after a bit of tuition were away with that and apparently my finning is good?

Next comes all the big gear and the mind game that because I have all this heavy gear on I need more weight to weigh me down (this all makes sense much later on during Ocean Diver Theory Lessons). Off we go up and down the pool and I’m absolutely loving it, kicking myself why didn’t I do a week’s course on holiday all those years ago.

All too soon it’s over and it’s back dressed in the pool café ready for what I assume to be the hard sell. To my surprise it never comes, the route forward is fully explained and when it comes to cost it’s a 3 figure number and not even a very high one and all the kit is thrown in free while I train??

I didn’t need to think twice and signed on for the next Ocean Diver course that was starting in a couple of months. Over the following 6 months I completed Ocean Diver & Sports Diver and can say the theory really drives things home about how & why you do things, something in hindsight I know I wouldn’t have taken in on a 1 week crash course on holiday.

So here I am just over a year & 50 dives into my diving and back to that original question, why did I take up scuba diving?10418415_928426427180405_3443156192959145676_n

Well, like hill walking I suppose there is a multitude of flora & fauna to see, different scenery wherever you go, but the best part for me is the feeling of isolation and comfort it brings, no modern distractions, mobile phones / iPads / no noise other than the bubbles from my regulator, no aches & pains in the joints as everything is nicely supported by the water. It’s a perfect switch off and reset from a busy week at work, the only things to think about are staying alive & keeping an eye on my buddy, the rest is just a sight-seeing trip.

I’m glad I took the BSAC route to diving as not only did it introduce me to a local club & a pool of dive buddies that I regularly dive with, but I liken the course to taking driving lessons one a week for 6 months or taking all of them in a week before your test, yes you can pass either way but how much sinks in in a weeks constricted course?

If you’re thinking of starting diving it’s never too late, the club I’m in ranges widely in ages and there is always someone either at your ability or willing to take you under their wing until you’re ready to fly. If you’re in the North West anytime and want to learn I’ll point you to as a good starting point.


Good luck



Very Early Pathe News footage (1958) of diving lessons theory & practical.

Various shots of naval divers getting dressed and entering the water at Whale Island Diving School. Several Shots of the divers in the water and as they finish the exercise.