As we get closer to opening our dive shop in less than a month, we will be writing various blog posts on different topics that may be of interest to both novice and experienced divers. For our first post, I would like to discuss the topic of buoyancy. I will first explain why good buoyancy control is the most important skill you can master as a scuba diver. Then, I will review basic scuba diving theory as it relates to buoyancy. Finally, I will give you some of my key tips that I use in training to help divers better control their buoyancy.
The theory sections are long and detailed, so that inexperienced divers can be reminded about concepts they may have forgotten or never properly learned. If you are a more experienced diver and would like to skip the theory to go straight to the tips, please click here. For any questions, comments, or critiques, feel free to submit a comment on this post. I will respond as soon as possible.
The Importance of Good Buoyancy Control
When I first started diving at age 16, it was not something I fell in love with straight away. The truth is that for my first 10 or 20 dives, I felt somewhat uncomfortable under the water. Most of the time, I was that unlucky soul who had to end the dive for everyone else because my air supply was low. I would struggle to control myself, constantly worried about bumping into coral and damaging the reef. Even though I enjoyed scuba diving overall, these frustrations weighed heavily on me each time.
As you could probably guess by now, my prior struggles underwater had everything to do with buoyancy control, or in my case lack thereof. Later on we will see specifically what was happening, and what I did to correct the problem. But for now let’s talk a bit about what buoyancy control is and why you should consider it to be the most important skill you can have as a diver.
For a diver, buoyancy control is the ability to control your body and relative position underwater. Good buoyancy control allows you to maintain a constant depth without worrying about unknowingly sinking to the bottom or floating to the surface. Many new divers can attest to how easy it can be to lose our orientation underwater if we aren’t paying attention. We may be at 10 meters depth, completely absorbed the beauty around us, then all of a sudden we are at the surface! This can be dangerous for a variety of reasons, including passing boats overhead and physiological risks of a rapid ascent. On the opposite extreme, I have seen cases of even experienced divers who unwittingly sink well below their planned depths. Good buoyancy control helps us avoid these problems.
An added benefit of having good buoyancy control is that we will expend less effort underwater. It helps us enjoy the dive more by maintaining a peaceful and relaxed state throughout. We not only feel more comfortable, but also we will use less air and be able to dive longer.
The Physics of Buoyancy
So how can we start to understand how to improve our buoyancy? In order to do that, let’s take a quick refresher on the physics of scuba diving (and see if you were paying attention during your Open Water Course!).
When we jump into the water for a dive, the first thing we do is push the inflate button on our BCD. This will add air to our BCD so that we are floating at the surface. In this case, we say that we are positively buoyant. When we are ready to descend, we hold up the BCD hose and push the deflate button. Now the air rushes out of the BCD until we start to sink, making us negatively buoyant. It is worth the reminder here that this is also why we wear a weight belt when we dive – to be able to sink. If we didn’t, the bulkiness of the BCD, westuit, and tank would keep us positively buoyant still. Also keep in mind that we should exhale as we start to descend. Less air in our lungs means we will sink easier (more about this soon).
Once we start to sink, then what happens to our buoyancy? As we sink deeper, we will become more negatively buoyant. In other words, we will start descending faster and faster as we reach greater depth. Why? The answer lies in the fact that we are generally wearing a wetsuit when we dive. There is a small layer of air within the neoprene fabric of the wetsuit that helps provide thickness and warmth. When we sink underwater, we are exposed to pressure. The pressure increases quickly as we sink deeper. This means that the air inside our wetsuit compresses, making it thinner and less buoyant. As a result, we will become more negatively buoyant as we sink deeper, all else being equal.
So what must we do to establish our goal of being neutrally buoyant underwater, so we are neither sinking nor floating uncontrollably? As you probably know already, we must add a little bit of air back into our BCD. This will provide positive buoyancy to counter-balance the increased negative buoyancy, theoretically making us neutral. Keeping in mind that if we go deeper, we may need to add a bit more air to compensate for the increased pressure. Vice versa, when we go shallower or make our final ascent, we must let some air out of the BCD. Otherwise, we will float up uncontrollably because the air already in our BCD, along with our wetsuit, will expand under decreased pressure.
That is the physics of buoyancy in a nutshell. Easy then, right? Problem solved and good buoyancy control achieved? Well, not exactly. I knew all of this theory just fine by the time I completed my Open Water Course, yet my buoyancy control still sucked. So now that we are refreshed on the basic physics, let’s get to the good part: tips for better buoyancy control!
1. Pay attention to your breathing!
I will preface this point by stating very clearly that this is what I consider to be the most important factor in good buoyancy control. Ignoring it is the reason I had bad buoyancy control at the start of my scuba diving career. But fortunately, once I started paying attention to this concept, my buoyancy got much better, and very quickly.
Have you ever tried to float in a swimming pool? If so, you will probably notice that you’ll have an easier time of it when you inhale a deep breath into your lungs. Your increased lung volume will provide positive buoyancy, making it easier to float. Exhale and you will notice yourself start sinking below the surface. When we are diving, we can use our breathing in much the same way. In a state of neutral buoyancy, we will float up a little bit when we take in a deep breath of air. Conversely, when we breathe that air out we will sink down a little bit.
My mistake, the same mistake I have seen many divers make, is that I would always try to adjust my buoyancy through use of the inflate/deflate buttons on the BCD. If I felt myself floating up at all, I would quickly raise the hose to release some air. Then I would inevitably feel myself sinking more than I wanted, and quickly rush to add air back into the BCD. I was entirely ignoring the fact that the cause of these minor changes in my buoyancy was likely nothing more than my breathing!
In reality, a diver should rarely need to adjust the air in the BCD during a dive. It is especially necessary when we change depths drastically, including on the descent and ascent. It may be necessary to compensate for increased buoyancy of the tank as it gets lighter on air during the dive. But besides that, we should rarely need to touch the inflate/deflate buttons of our BCD during a dive.
Instead, we can really fine-tune our buoyancy by paying attention to our breathing. If we are approaching a coral that we want to go over top of, we can time our breathing to inhale deeply right before the moment we want to float up. Then, we can exhale deeply to come back down on the other side. Be careful not to hold your breath! We know from the most important rule in diving that we cannot do that for risk of lung expansion when ascending. But if you time your breathing the right way, you will be able to master buoyancy control with little to no effort involved.
Keep in mind that it usually takes a second or two after the breath for your body to react, so try to get a feel for the timing. With a little practice, the technique becomes so natural that you won’t even have to think about it. You will simply adjust your breathing naturally based on what you want your body to do.
2. Use a proper amount of weight
We touched previously on the purpose of the weight belt, namely to make sure we sink when we let the air out of our BCD at the start of a dive. Does that mean you should strap on as much weight as you can find to make sure you will sink? Of course not. In reality, we should strive to use just the right amount of weight to allow us to sink below the surface with a deflated BCD, and no more. As we already reviewed, we will only become more and more negatively buoyant as we sink. So no more weight is necessary other than the amount that will get us under the surface to begin with.
There are many divers, even experienced, who are constantly diving overweighted. There are significant drawbacks to this. For one, you will have to add more air to your BCD to achieve neutral buoyancy at depth. This means that if you change depth even slightly after that, there is a lot of air inside the BCD that will expand or compress. Therefore, you will have to continue adjusting the BCD a lot more than if you were properly weighted. It also means that since you need to add more air to be neutrally buoyant, you will be bulkier underwater. As a result, you will need to use more energy during the dive, potentially getting low on air quicker. As most divers wear weights on their hips, overweighting has the added drawback of dragging down the lower half of your body, making it harder to maintain proper trim (body position) underwater.
How do we know how much weight is the proper amount? You should have done something during your Open Water Course called a buoyancy check to address this. During a buoyancy check, you float vertically and motionless at the surface, holding a normal breath of air in your lungs. Then you let all the air out of your BCD. If you are properly weighted, you should: 1) float at eye level, and 2) start to sink when you exhale the breath. That tells us exactly how much weight we need to descend, and no more.
Keep in mind that if you do a buoyancy check with a full tank, it may be necessary to add an extra kilo or two to compensate for the fact that the tank will lose buoyancy as you use air during the dive. Otherwise, come time to make your safety stop at the end of the dive, you may find yourself starting to float up a bit. Also keep in mind, if you ever change diving conditions, diving equipment, or have been out of the water a long time, it is best to do another buoyancy check as your optimal weight may vary based on those factors.
3. Maintain proper trim
Trim is referring to a diver’s body position. Underwater, our ideal trim as divers is that we are in a completely horizontal position with our arms stationary. That way, we can easily kick ourselves through the water maintaining constant depth.
Oftentimes, I see divers whose legs are dragged down below the rest of their bodies. For some newer divers, this is because the horizontal position may feel unnatural at first. Or, it could be due to overweighting your belt, as we mentioned previously. Whatever the reason, the result of such bad trim is that we may kick the bottom, damaging the environment or impeding visibility by stirring up sand. Or, we may constantly kick ourselves up in depth, making it necessary to adjust buoyancy frequently throughout the dive.
If you are having issues maintaining proper trim, try redistributing some of your weight to your upper body. You can use the tank strap for this, either by threading a weight directly on to it or using specially designed weight pockets that clip to the tank strap.
4. Use visual references
It is important to use our visual references effectively to ensure we are aware of our position and surroundings. This way, we will notice slight changes in our buoyancy before we float all the way up to the surface, or sink below our intended depth. An important visual reference to use is your dive guide and/or dive buddy. It can be easy to lose yourself in the beauty of your surroundings underwater. But you should be constantly aware of the divers around you as well. It is not only to keep the group organized and together, but also to notice if you unintentionally change depth in relation to the other divers. That way you can adjust your buoyancy before your depth changes even more drastically.
It is also useful to use natural visual references. For example, if you glance at the bottom every now and then, you will be able to know if you are floating up too much or sinking too close to the floor. If you are on a wall dive, use visual references on the wall to help maintain constant depth.
5. Notice when you are kicking chaotically or flailing your arms
Most divers know that scuba should be a relaxing and peaceful experience. When we see divers underwater who are constantly flailing their arms or kicking chaotically, it is obvious that something is wrong. But do we notice these same tendencies in ourselves?
The first time I saw a video of myself underwater, I could not believe how much I was doing this without even realizing. These jerky movements in our arms and legs are futile attempts to correct bad buoyancy. In reality, we should never need to use our arms when we dive. Doing so is simply a waste of effort. Additionally, we should strive for gentle, relaxed, near-effortless kicking. Our fins are powerful enough that we should not need to do anything more than this. If we find ourselves wasting energy unnecessarily, it is likely we need to revisit the previous points to correct the underlying issue of bad buoyancy control.
Hopefully these tips help you to perfect your buoyancy control. In our opinion, it is undoubtedly the most important skill you can have as a good diver. Any questions, comments, or clarifications, feel free to leave a comment and we will address it!