FayObserver.com published an article yesterday on sharks and scuba divers. The article is a part of a common attempt to dispel the myth of man-hunting sharks.

One diver interviewed for the article, Hank Parfitt, frequently swims alongside shark, and even acts as a shark wrangler for underwater photo shoots. The most practical bit of the article is Parfitt’s tip on giving an angry shark its space.

When is a shark angry? Parfitt gives three signs:

1. Pectoral fins angled down. A neutral to happy shark will swim with its pectoral (side) fins straight out, like an airplane. If you see them angled down, the shark is upset, hungry, defensive, or some non-friendly emotion. Give it some distance.
2. Arched back. My guess is that an arched back is like a spring, getting the shark ready to dart at potential food or something it feels may harm it.
3. Shaking its head back and forth. In conjunction with the previous two, a shark shaking its head like it’s saying “no” is not happy and may be aggressive.

Calm sharks are easy to observe. A few brave like Parfitt will even touch the shark, but always in front of the dorsal fin. Like all animals, the rear is particularly vulnerable, so avoid sneaking up on a shark (even if it’s unintentional). When treated with the respect they deserve, scuba diving with sharks can be a great experience.

The first place I ever dove after certification was Bermuda. On one boat dive we were briefed by the divemaster in preparation for our first dive. He asked if there were any questions.

“Yeah, should we make a safety stop”, I asked. Fresh out of my checkout dives, I couldn’t remember the rules for when to make a safety stop.

The divemaster scoffed at me. “We’ll hardly be going deep enough to require a safety stop.”

Fast forward a few years. I’ve read a mountain of material for fun and as part of my professional development. Looking back on this occasion, what would I have done knowing what I know now? I most definitely would’ve made a safety stop.

In case it’s been a while since you’ve had one, a safety stop is an approximately three minute stop made at 15-20 feet (5-7 meters) at the end of a dive. For deeper dives greater than 60 feet / 20 meters, they are usually considered a requirement, and optional for anything less.

The idea is that this brief time at a relatively shallow depth will eliminate a large amount of microbubbles, an effect strongly correlated with decompression sickness. Studies have shown that a safety stop eliminates virtually all detectable bubbles, decreasing the chances of decompression sickness drastically.

I’m sold.

In fact, unless I’m short on air or in a hurry, I always make a safety stop. Even for 50 foot dives. If you have a proven way to decrease your risk, why would you not?

I don’t blame the Bermuda divemaster for what he said. If there is ever a time when it is perfectly reasonable to forego a safety stop, it is on the first dive of the day (unless it’s a deep dive). Nevertheless, I see no reason to scoff at the suggestion, as they are something everyone should take seriously and include in their dive planning.

Photo by tslane888

A year ago I was working in New Zealand. I was interested in what the local diving had to offer, so I signed up for a small trip off the local coast of Wellington. What happened on that trip turned out to be a valuable learning experience.

It was a cold morning when we pushed off from shore in a small fishing boat, six divers and two crew. I was a little nervous since I knew the water would be cold—it was winter there, after all. I wore an old, uncomfortable rented wetsuit. A farmer john that had seen more than his fair share of divers. Add in the unfamiliar equipment and all weights and cylinder measured in that odd system known as metric, and I was in an uncomfortable place to start a dive.

Once on the water the captain asked us each to introduce ourselves and briefly outline our experience. As we went around, I quickly realized I was the most unseasoned diver on the boat. Everyone else had hundreds, some thousands, of dives, most in the murky Wellington waters. Despite having recently completed my rescue diver certification, I was feeling a little intimidated when I had to announce my meager dive experience.

I was teamed up with Tom, one of the highly experienced divers, and a nice guy to boot. We did backrolls into the choppy water. With the new equipment and unfamiliar waters I was unsure of my weighting. When grabbing my weights in the shop, I had no idea how many to use. Not only were they in kilograms (although I knew the rough conversion), I had all new equipment and did not have a good starting point. I asked around what others were wearing, but I couldn’t use anyone remotely close to my size’s weights as a guide (for example, one diver had a steel plate in his BCD).

Time to descend. Instead of stopping Tom and doing a proper weight check, I didn’t want to look like an amateur and descended anyway. As soon as I slipped beneath the surface I knew I had made a mistake. Not a great way to start a dive.

Despite this ominous feeling, the dive went off without a hitch. I was cold and burning through air faster than Tom. I felt bad that I was limiting our dive time, but when my air got low, it was time to end the dive, but first, a safety stop at 5 meters.

During the safety stop I started to feel the effects of not being properly weighted. As my tank emptied, it became more buoyant, requiring more weight to stay underwater—weight that I didn’t have. Only a minute in and I was struggling to stay underwater. In fact, I was completely upside-down kicking to stay at safety stop depth. Unable to fight the buoyancy any more, I floated to the surface right before the end of the requisite three minutes, while my confused buddy watched from his safe depth.

In an attempt not to embarrass myself and look like an “amateur”, I ended up embarrassing myself far worse. Fortunately, my dive buddy was gracious and did not say anything as I found more weight for the next dive. I realized my stupid mistake and swore I would never put myself at risk again for the sake of looking more experienced. This time it wasn’t a big deal, but next time it may be in a more unforgiving environment.

No matter how little or how much you dive, there is nothing embarrassing about being safe and comfortable on all your dives. If your buddy or anyone else has a problem, then it is their problem, and you can rest assured that they’ll be the ones who end up looking inexperienced. No diver worth their salt would belittle you for being a safe and cautious scuba diver.

Photo by JennyHuang

Snorkels are considered a core piece of scuba gear. Mask, fins, and snorkel: the three items every beginner starts with. We take this for granted, and dive away with those plastic tubes strapped to our head. After a while, though, we start to question the utility of a snorkel. When diving the smooth Caribbean waters, for example, is a snorkel really necessary?

At this juncture, there are a few paths the blossoming diver can take:

• Keep the snorkel. Your first option is to heed your training and continue to dive while wearing a snorkel at all times. Sure, it can be uncomfortable in a current, but you rest easy knowing it’s always there.
• Exchange the snorkel for a pocket snorkel. Your next option is to remove the snorkel from your mask. Aaah, how liberating! There are times when you may need a snorkel, so for those situations you carry a foldable pocket snorkel in your BCD pocket. In an emergency, it’s only a zipper away.
• Ditch the snorkel. Look out, divers, this future tech diver means business! The last option is to ditch the snorkel completely. I don’t imagine anyone throws their snorkel away, but rather keeps it in their gear bag and wears it on a case-by-case basis. Choppy waters with low viz? Bring the snorkel. Bonaire shore dive? No thanks.

If you find a snorkel uncomfortable, I think carrying a pocket snorkel is your best option. I don’t own one (yet), so I wear a snorkel based on the dive conditions. However, be aware that some dive operators may not let you in the water if you don’t have a snorkel. For this reason, you should always carry a snorkel with your gear.

What do you think? Are snorkels for sissies, or would only a fool go in the water without one?

Photo by chrisada

As a scuba diver, theoretical knowledge cannot always be immediately recognized as useful. It does, however, come in handy. If you decide to move on to a professional level of certification, theoretical knowledge development is a requirement. It can also provide understanding behind practical decisions, guiding your reasoning in a more educated manner than just following a set of rules. Today we’re going to talk about the biggest theoretical area there is for scuba divers, decompression theory.

The need for decompression theory arises from decompression sickness (DCS). DCS encompasses the illnesses that may occur from the body’s exposure to varying pressures. This is not strictly limited to scuba divers, but clearly we have a highly vested interest in the development of sound theory to describe the causes, effects, and preventions of DCS.

I say this, because the discovery of DCS predates recreational scuba diving by about 100 years. There is documentation of DCS symptoms as early as the 1840s, where workers in pressurized French mines fell ill with the now-recognizable effects of “the bends.”

It was well over 60 years before enough progress was made for any practical advantage. In 1906, the British Royal Navy commissioned physiologist John Scott Haldane to study DCS. He built on the work of Paul Bert who, years earlier, made progress in identifying the cause of DCS. In particular, it was Bert who named dissolved nitrogen as the culprit in DCS. However, it was Haldane who built the first complete theoretical model.

Haldane and his team experimented with goats in pressure chambers. This research led him to describe a theoretical decompression model and build the first dive tables that could be verified experimentally. Today, over 100 years later, practically all dive tables and dive computers are built upon this original Haldanean decompression model.

Decompression models

A decompression model is some theory you can follow and apply in order to decrease your risk of DCS. A model is only as good as it has been verified to prevent DCS. There are too many factors involved to currently guarantee prevention. As they say, the only way to 100% prevent DCS is to not dive. Aside from that, there are models that have been in use for a very long time (like the Haldanean model) and have been shown to decrease your risk of DCS drastically.

Ideally, a model is developed through scientific means—by studying the physics and physiology of the human body. It doesn’t have to be, though. For example, a model followed by early divers was “the 50 rule.” This “model” dictates that the depth (in meters) and time of your profile should add up to no more than 50. A 10 meter dive for 40 minutes, 20 meters for 30 minutes, and so on. This actually wasn’t a terrible model, although there is no real theory behind it. You’ll notice that it is overly conservative, though. This guides continual research into model development—getting you the maximum dive time in the safest way possible.

Haldanean model

Building on the observation that dissolved nitrogen triggers DCS, the Haldanean model is build around a few principles:

• Nitrogen dissolves into tissues. After enough time, the tissue becomes completely saturated. This is Henry’s law.
• The tissue will reach saturation determined by the ambient pressure. So a given tissue under higher pressure contains more nitrogen than the same tissue at the earth’s surface.
• The difference between the ambient pressure of nitrogen and a tissue’s partial pressure of nitrogen is called the pressure gradient.
• When ascending, the dissolved nitrogen’s partial pressure may be higher than the ambient pressure. The body can tolerate some amount of pressure gradient without DCS.
• If the pressure gradient becomes too high, the dissolved nitrogen cannot be eliminated quickly enough. Nitrogen bubbles form, leading to DCS. Thus, the risk of DCS can be reduced by keeping the body’s pressure gradient within acceptable limits.

To understand these ideas better, we need to review a few concepts.

Partial pressure

Recall from our article on enriched air / nitrox the idea of partial pressure. Total ambient pressure at sea level is 1 atm. Therefore, the air we are breathing is also at 1 atm. This air is comprised of mainly two components: 21% oxygen and 79% nitrogen. We can say, then, that the partial pressure of oxygen at the surface is 21% of 1 atm, or .21 atm (some people write this as .21 PPO, for partial pressure oxygen).

Likewise, the partial pressure of nitrogen at the surface is .79 atm. This principle is captured by Dalton’s law, which states that the 1 atm of pressure at the surface can be written as the sum of the partial pressures, .79 atm nitrogen + .21 atm oxygen = 1 atm total.

This is all at sea level. The deeper we go, the higher the pressure, and the higher the resulting partial pressures. At 10 meters depth, the pressure is 2 atm. By Dalton’s law, the partial pressure of nitrogen is 1.58 atm and for oxygen is .42 atm (notice how they both add up to 2 atm).

Mainly what this means is that the deeper you dive, the more nitrogen you absorb with each breath.

Tissue compartments

Haldane’s model is built around how the body’s tissues absorb and release nitrogen. There’s just one problem: the body is incredibly complex, and accurately modeling all its tissues is not a tractable problem, not even now, much less over 100 years ago.

What Haldane could determine was that different parts of the body absorb and release dissolved nitrogen at different rates. Instead of attempting a much larger problem, he simply represented the entire body by a number of theoretical tissue compartments. These are called “theoretical” because they don’t correspond to any particular tissue in the body, but rather attempt to capture the idea that the body absorbs nitrogen at different rates. Together, these theoretical tissues are meant to represent the body as a whole and the time scales at which it deals with nitrogen.

Haldane originally used 5 compartments. Later, the US Navy dive tables used 6. Some modern tables use as many as 14. There is no limit to the number of theoretical compartments, but any advantage they may provide rapidly falls off as you add more.

Halftimes

These theoretical tissue compartments (from now on, just tissues, or compartments) represent the different rates different parts of the body absorb and release dissolved nitrogen. The model must then deliver these rates. It does so, in the form of tissue halftimes A tissue halftime is the length of time it takes for a given compartment to halve the pressure gradient.

For example, if a compartment contains absolutely no dissolved nitrogen, and is exposed to air at 1 atm, its halftime is the amount of time until the partial pressure of nitrogen in the tissue is .395 atm (half of the partial pressure of the nitrogen in the air, .79 atm / 2 = .395 atm).

Saturation is reached when the pressure gradient is 0, or the partial pressure of nitrogen in the air is the same as the partial pressure of nitrogen in the tissue. This means after one halftime a compartment is 50% saturated. It is not 100% saturated after two halftimes, since each time the pressure gradient is halved, so after two halftimes a compartment is 75% saturated. After three, 87.5%. Four, 93.8. For simplicity, we say a compartment is 100% saturated after 6 halftimes (it’s actually 98.4%, but that’s close enough).

The US Navy model uses 6 compartments with halftimes of 5, 10, 20, 40, 80, and 120 minutes.

Examples

Halftimes can be confusing, so let’s look at examples. For further simplicity, we refer to a compartment’s saturation level in terms of depth. We definitely wouldn’t say 50% saturated, since that gives no indicated of the partial pressure. Similarly, we don’t say the tissue has 1.185 atm nitrogen, although you could. Instead, we give the depth corresponding to that partial pressure of nitrogen. In this case, the partial pressure of nitrogen in air is 1.185 at 5 meters. So we say this compartment has a nitrogen loading of 5 meters (this is also written as meters /feet sea water, or msw / fsw).

Imagine a dive to 20 meters for 40 minutes. What do the 6 compartments look like? For the 5-minute compartment, 40 minutes is 8 halftimes. Recall that we consider 6 halftimes as reaching saturation, so the 5-minute compartment is completely saturated, and has a nitrogen loading of 20 meters.

The 10-minute compartment has gone through 4 halftimes. After the first halftime, its loading is 10 meters. After the second, 15 meters. Third, 17.5 meters. Fourth, 18.75 meters.

The 20-minute compartment has completed 2 halftimes, so it is at 75% saturation, or 15 meters. The 40-minute tissue has completed one halftime, so 10 meters. The 80-minute has completed half of a halftime, so 5 meters. The 120-minute compartment is at 3.33 meters.

M-values

Notice something interesting about what we’ve covered so far. Nowhere has there been any indication on how this model guides your dives. That’s because it doesn’t! To decrease our risk of DCS when ascending, we have to keep a tissue’s pressure gradient below an acceptable threshold. The model so far has not given these thresholds.

These thresholds can only be obtained experimentally. That’s what we’ve done over the years. After thousands of controlled dives and observing symptoms at the surface, scientists obtain values for acceptable pressure gradients for each theoretical tissue. These values are called M-values.

There are M-values for each compartment for each decompression stop. In no-decompression diving, however, we only have to be concerned with the values for the pressure at the surface, which are sometimes written as “M₀-values.”

Dive table designers can experiment with different M-values, but they should be consistent with the data. If experiments show that exceeding a certain value for a given compartment usually results in DCS, then the final table should limit dive profiles based on that value.

A complete model

We now have all the tools for a complete model. A set of compartments with their halftimes, as well as an M-value for each compartment. Let’s do an example.

Let’s use the same compartment halftimes with M₀-values of 30 meters, 20 meters, 15 meters, 10 meters, 7.5 meters, and 5 meters. This means that the 5-minute compartment should not exceed a nitrogen loading of 30 meters, the 10-minute compartment should not exceed 20 meters, and so on.

With our dive to 20 meters for 40 minutes, our tissue loadings were 20 meters, 18.75 meters, 15 meters, 10 meters, 5 meters, and 3.33 meters. Uh-oh! Our 20-minute and 40-minute compartment have reached their M-values (15 meters and 10 meters). That means it’s time to end the dive or ascend to a shallower depth.

If we ascend shallow enough, the 20-minute and 40-minute compartments, even when saturated, can never exceed their M-values. So as long as we ascend shallower than 10 meters, the 40-minute compartment can never exceed it’s M-value. From this we notice that shallower depths are controlled by slow compartments (high halftimes), while the fast compartments (short halftimes) control deeper dives.

For instance, the 5-minute compartment will reach its M-value very quickly at deep depths. At 40 meters (the recreational limit), one halftime (5 minutes) will load the compartment to 20 meters. Another 5 minutes will have it at 30 meters. Staying at 40 meters any longer will require decompression stops.

Keep in mind that following this model with these M-values does not provide any guarantee that DCS won’t occur. It can still happen, although many years of diving with established tables has shown that the chances are minimal. Still, it doesn’t hurt to dive conservatively.

Conclusion

Phew! That was a lot of material. Give it a little time to sink in. We’ll pick up where we left off in future articles. For example, what about repetitive dives? How do compartments release nitrogen when we are out of the water? At the same rate that they absorb?

We’ll also look at how this information can be used when purchasing a dive computer. Stay tuned!

Feel free to ask any questions or add to the discussion in the comments.

Probably the biggest source of confusion during a rescue diver course is the creation of an emergency assistance plan. Students aren’t sure how much or how little to include. They aren’t sure they did it right when it doesn’t take a long time. This article is meant to clear up these problems.

First of all, I’m going to say that creating an assistance action plan should not be a terribly difficult exercise, especially in the internet age. There are a few key components that should be included along with a few optional items. Finding this information these days should be a breeze. Before we get into what exactly to include, let’s discuss the purpose of an emergency assistance plan. This should illuminate exactly what is required to construct a complete plan.

Purpose

The purpose of an assistance plan is simple: in the case of an emergency, an emergency assistance plan should assist an uninformed bystander in contacting emergency services and getting them to the location of the accident. Right away this should clue you in on what’s required. In fact, putting too much information will only slow things down during an emergency situation.

In general, there doesn’t have to be too much detail in an emergency plan. However, courses usually require plans for a specific dive site. This is probably an additional source of uncertainty. If in doubt, just ask your instructor how specific everything should be. Additionally, consult your textbook for any insights it may offer.¹ Though it never hurts to put in too much information, at least for the sake of fulfilling a course requirement.

What’s in it?

Now we know what the overall purpose of the plan is, but what exactly do we put in it? This is what everyone wants to know. After considering the purpose, we can ask some questions to discover what should be in this elusive little document.

If a diving emergency was taking place around you, what information would you need to be of some assistance? Clearly, we need some sort of contact information for the local emergency services. In particular, we want scuba-related contacts. If your diving locale has an emergency hotline dedicated to scuba emergencies, include that as well as general emergency numbers.² Look up the local Divers Alert Network (DAN) for their contact information.

This information (local EMS plus any scuba-related EMS) is the core of your emergency assistance plan. You can’t get away with less. There is, however, plenty more you could include for absolute completeness. What other information could be useful during an emergency?

Sometimes it may be faster to transport the injured yourself. For this reason, I like to include the location of the nearest hospital, possibly with a map or directions. A contact number for the emergency room is also good, to alert staff that you are on your way with an injured diver.

The location of nearby emergency equipment is also pertinent. This includes things like emergency oxygen and first aid kits. Often, EMS may take a while to arrive, costing your victim precious minutes. Being able to help in the meantime by administering oxygen or basic life support could be the difference between life and death. You may know where the oxygen tank is, but if you’re busy giving rescue breaths, you want someone else to be able to retrieve it.

Depending on where you are diving, the location of the nearest telephone may be useful. Imagine if a foreigner was responsible for contacting emergency services after an accident. They have your emergency assistance plan, but no local mobile phone. It could be when you handed them your plan you told them to use your phone, but if diving remotely this may not always be a possibility. It’s location-specific, and definitely something to think about, but not required.

My rescue instructor was fairly stringent and required that I include a script for someone to read when calling emergency services. The key parts of this script are your location (not just the dive site name, but where it actually is), and that this is a scuba diving related emergency. This bit of information could change the reaction of emergency services on the other end. For instance, they may realize that a decompression chamber is needed and avoid hospitals that aren’t equipped to handle decompression sickness, saving valuable time.

Another optional item is a map of your diving location that identifies all the important landmarks nearby, such as the emergency equipment, telephones, and even the hospital. This diagram of the dive site could be useful in an emergency, but is usually not required. If your instructor doesn’t request it, you can still include it for brownie points.

Templates

To save you some time, I created a free emergency assistance plan template. Fill out as much or as little as you (and your instructor) think is necessary, replacing the text inside the <brackets>. Delete the rest. Click the following links for the format of your choice:

iWork Pages
Word 2007 & 2008 (.docx extension)
Word 97 – 2004 (.doc extension)
Adobe PDF
Rich Text Format

My hope is that this article (and the templates) take some of the mystique out of creating an emergency assistance plan. This is something you’ll probably only have to do twice during all your training (for rescue diver and for divemaster), but it is good to know the thinking behind it’s construction and the overall purpose it serves.

Time to help me out. Is there anything critical I left out that should be in an emergency assistance plan? Let me know in the comments.

1. I can’t say for other agencies, but the PADI rescue diver manual is nearly useless for information about creating an emergency assistance plan.
2. Funny story. I did my rescue diver course in New Zealand. For my assistance plan, I wanted to include the telephone number for a local hospital. I found the hospital, looked the number up online, and put it in my plan. During the course, everyone except me noticed something wrong with the hospital’s number, +44 xxx-xxxx. Turns out the hospital was part of a UK conglomerate, and the number I found was for their main London hospital. Being a dumb American, I put the phone number with the UK country code for my New Zealand dive plan. Go me.

The time has come. I’ve been toying with the idea for a while, but I’ve finally taken the plunge and signed up or scuba diving insurance.

Why insurance?

I dive more than three times a year, and plan to dive frequently in the future. It’s said that the only way to prevent decompression illness (DCI) is to not dive, so it makes sense that the more you dive, the more risk you incur. You can follow every table or computer to the letter and still get sick.

I know I sound like an insurance salesman, but when you purchase insurance, you are purchasing peace of mind. DCI is expensive, especially if they have to helicopter you off a boat. To make matters worse, most insurance policies don’t cover scuba diving accidents, so you can easily accrue tens of thousands of dollars in debt from a single incident!

Check your policy. Find out if you’re covered. You’ll probably find that you’re not as protected as you thought. For me, the small cost per year is well worth the peace of mind.

How?

I’m sure many companies will be happy to underwrite you for additional coverage. For most people, however, the easiest way to get coverage is through the Divers Alert Network (DAN). DAN is a non-profit medical and research organization that supplies resources for recreational divers.

I signed up for insurance through DAN and it was easy. There are only two steps:

1. Become a DAN member

   Only DAN members are eligible for insurance. This comes with some perks like a subscription to their magazine, but nothing I was terribly interested in. Individuals pay $35 a year for membership or you can subscribe your household (people with the same mailing address) for $55 a year (these prices are current as of 2010 and in US dollars).

2. Sign up for DAN insurance

   Once you have membership, you can immediately sign up for insurance. DAN offers three insurance programs: the standard plan, the master plan, and the preferred plan.

   The standard plan is rather skimpy, which is reflected in the $25 a year cost. There is a $45,000 lifetime maximum payout for the plan.

   The master plan is a little better, offering a $125,000 lifetime maximum payout. It includes a few additional items, such as payment for lost diving equipment, dismemberment (yikes!), and disability. For these additional benefits the price goes up to $35 a year.

   The preferred plan offers $250,000 coverage per incident. It includes slightly higher payouts for each item compared to the master plan, but the cost doubles to $70 a year.

I went with the Goldilocks plan, right in the middle. It balanced decent payout with a cheap yearly cost. For individual membership in the master plan, you’re facing $35 + $35 = $70 a year: a perfectly reasonable cost for active divers.

The entire process took less than 15 minutes, including signing up for DAN membership. DAN will want to know who your primary insurance provider is since some parts of a diving incident may be covered by your primary plan, so you may want to have that information at hand.

DAN is a US organization, so this only applies to American divers. I’m curious about divers from other countries, particularly those with public health care: does your healthcare cover diving accidents, along with hyperbaric treatment, or do you take out private insurance?

Skip-breathing is briefly holding your breath between inhales / exhales. Theoretically, it could cause hypercapnia, or excess carbon dioxide in your blood. Serious complications from skip-breathing seem unlikely, nevertheless it is a bad habit that should be avoided. Why would someone do it?

• Unconscious activity

  Sometimes we do things without even thinking about it. Any habit formed during basic certification could easily persist without any conscious effort. Force yourself to become conscious and it won’t take long to break the habit.

• Trying to save air

  The less you actively breath the less air you use, right? Wrong. Holding your breath, even momentarily, raises the amount of carbon dioxide in your body, which requires more oxygen to flush. The net effect is that any savings in air usage are cancelled, or become negligible.

• Trying to control buoyancy

  I’m guilty of this one, especially during fin pivot exercises. Fine tuning your buoyancy through breath control is natural, and expected. However, breath control does not equal breath holding. Rather than holding your breath, practice achieving the same effect through shallower breathing.

Slow, controlled breathing is best, while any form of breath holding, even skip-breathing, is not recommended. Try to keep your breathing non-stop throughout, and watch how quickly good habits are formed.