There’s one dive skill that you’ve been doing way before you even became a scuba diver: breathing. You’ve been doing it all day, every day from the moment you’ve been born, and I’m guessing it has worked out pretty well for you so far. So it can come as a surprise when I tell you that your breathing technique may not be as good as you think it is!

Breathing is the very essence of scuba diving. If you’ve ever wondered where the word SCUBA comes from: it stands for Self Contained Underwater Breathing Apparatus. The tank and scuba gear allow you to do the impossible: breathe underwater. Without that, there’s nothing SCUBA about it, it would just be diving! So if you want to be a good scuba diver, you better learn how to breathe right.

In the last part of the Scuba Fundamentals Series we discussed buoyancy control and how to improve it. Breathing and buoyancy control are one and the same. Without controlling your breath, you can’t possibly have good buoyancy control!

Why most divers don’t use the right breathing technique

When you first start out diving, it can be pretty overwhelming. With so many things to think about, breathing is probably not at the top of your list. That makes total sense, because you do it automatically. But that doesn’t mean you’re doing it right! When you’re unaware of your breath, you tend to take shallow breaths from the chest area. In normal life, that usually doesn’t cause any problems. But when dealing with increased gas densities and dead air spaces as we do in scuba diving, incorrect breathing techniques can suddenly have serious consequences.

Why your breathing technique is so important 

Alright, so you may not be doing it completely right, but you’re still alive, so who cares right? Actually, no. First of all, your breathing technique impacts your air consumption, and this determines the duration of your dive. Bad breathing technique means that you probably ‘waste’ a lot of air and therefore consume it much faster, making your dive time shorter. So if you want to get the most out of your dives, improving your breathing technique is the way to go! This is pretty common knowledge, but not many people are aware that incorrect breathing can also have more serious consequences like narcosis, decompression sickness and oxygen toxicity.

Your lungs and gas exchange

To understand this, it’s important to know how our lungs work. I won’t go in too much detail here but simply put, gas exchange takes place in the lower half of our lungs. Which is why you want to let your air spend as much time there as possible. Gas exchange goes two ways: on the one hand your body absorbs the oxygen you inhale, and on the other hand it releases carbon dioxide when you exhale. Without proper breathing technique, gas exchange becomes ineffective: you don’t absorb enough oxygen and you don’t release enough carbon dioxide. It’s pretty obvious how a lack of oxygen can be a problem: we need it to survive. In fact, our body can only survive for four to six minutes without oxygen!


But the effects of excessive carbon dioxide in our body are probably less known. There are several reasons why carbon dioxide buildup can cause serious problems. It’s more narcotic than nitrogen and also has a more dramatic narcosis, which could lead to panic. It also increases the risk of decompression sickness and oxygen toxicity. On top of that, carbon dioxide build up has an exponential effect: it sends a signal to your brain that tells it to breathe more rapidly, often resulting in more shallow breaths in the upper half of your lungs (hyperventilating), only making the carbon dioxide buildup worse.

The whole process of how gas exchange works exactly, and how ineffective gas exchange can cause problems is of course much more complicated than how I explained it here. If you want to learn more about this process, I encourage you to do so! But hopefully you already understand the importance of a correct breathing technique, so let’s see how you can actually accomplish that!

Ideal breathing

Mastering a correct breathing technique is also called ideal breathing in scuba diving. Ideal breathing provides the best gas exchange possible by allowing the air you breathe to spend enough time in your lungs for oxygen to be absorbed, and for carbon dioxide to be exuded. In your Open Water Course you’ve probably learned that you should breathe slowly and deeply, but do you actually know what that means?

Ideal breathing means that you need to breathe from the diaphragm, a muscle that separates the abdomen from the chest. When inhaling, you pull the diaphragm down and away, by expanding your belly. You fill your lungs by drawing air in from the bottom of your lungs and letting it out from the top. Keep inhaling until your lungs are completely full, pause, and release the air slowly. Throughout this process, you want to keep the lower part of your lungs filled for as long as possible. If you find this difficult, try placing a hand on your belly and expanding it while you inhale.

Tip: placing your tongue against the top of your palate will help you to slow down your exhalation. Exhaling should take longer than inhaling.

Ideal breathing is not difficult to master, but it does take awareness. This is often the biggest challenge, especially for new or nervous divers. Do you have to practice ideal breathing at all times? No, it’s ok to deviate from it, as long as it’s by choice – for example to compensate for changes in buoyancy. But to be able to make that decision, you first need to be fully aware of your breathing technique.

How to track your air consumption

Now that you know how to improve your breathing technique, it’s time to start tracking your progress. This can be done by calculating your Surface Air Consumption Rate (SAC).

SAC = consumed air / total dive time / pressure of average depth

Even though the formula may seem a bit intimidating (at least it does to me), it’s actually pretty easy to calculate.

Let’s take a look at the following example: a diver has started his dive with 200 bar and an 11 liter tank. His total dive time was 38 minutes and the average depth of the dive was 12 meters. At the end of the dive he had 90 bar left in his tank.

Because you may not always dive with the same tank size, you first need to convert the consumed pressure to liters. If you really have no idea what tank size you’ve used, you can skip this step. Your results will be less accurate, but it still gives you a pretty good idea of your progress. And if you always dive with the same size tank, it won’t make any difference at all!

Step 1

  • Start pressure – end pressure = consumed pressure x tank size in liters
  • 200 bar – 90 bar = 110 bar x 11 liters = 1,210 liters consumed on this dive

Because you consume air at a different rate depending on your depth, you need to convert the average depth to the surface equivalent volume. You can find the average depth of your dive on your dive computer.

Step 2

  • Pressure of average depth = (depth / 10) + 1
  • (12/10) + 1 = 2.2

Now you’re ready to make the final calculation!

Step 3

  • Consumed air / total dive time / pressure of average depth
  • 1,210 / 38 / 2.2 = 14.47 Surface Air Consumption


Although there are certain factors that can influence your SAC on a single dive, such as comfort level, water temperature or currents, you will probably see your personal SAC improve over time. But before you start bragging about it to your fellow divers (please don’t do that – it’s really lame), I want to stress that there is no such thing as good or bad air consumption. Sure, your air consumption can be high or low, but if that’s the amount of air you need for your body to keep functioning, then that’s what it is. 

How much air you breathe to supply your body with the oxygen it needs, depends on many factors: your lung volume, body size, fitness level, muscle/fat ratio, whether you smoke or not, your comfort level, level of exertion, and much more. So instead of comparing yourself to other divers, take a look at your personal progress. If it’s not improving over time, or if you really feel like your air consumption is much higher than it should be, there could be an underlying problem. Maybe you’re carrying too much weight. Maybe you’re very anxious when diving. Or maybe you really do need to work on your physical fitness. You probably want to address those issues – not to improve your air consumption, but to make your dive experience better in general.

logging your sac

The perfect way to keep track of your SAC is by logging your dives. That way you can also make note of other factors that may have influenced your air consumption to be higher or lower than usual, such as a strong current. I like to log my dives in Google Sheets: it’s simple but very effective and it automatically calculates my SAC for each dive. I’ve made my dive log template available for free! Just fill out your email address below and I’ll send you the link.


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