Buoyancy is often one of the difficult skills to get right for beginner divers, but once you get it, it just makes sense. Here are a few tips to help you master your buoyancy skills.
Your Low pressure inflator is not an elevator button
Divers often think that the way a BCD works is to take you up when you want to ascend and to take you down when you want to descend. A friend of mine once used a very good phrase, reminding her students that a BCD/low pressure inflator is not an elevator button.
The function of your BCD is to make yourself neutrally buoyant in the water, thus you want to compensate for the weights that you are wearing by adding air to the BCD. By doing this you want to create a situation where you are practically weightless in the water. At the same time you do not want to inflate your BCD too much, causing you to feel unstable and ‘light’ during your dive.
By making yourself neutrally buoyant or nearly weightless in the water (this is achieved by adding a little bit of air to your BCD) you can use your fins and powerful thigh muscles to move yourself in the water.
Ideally you would use your BCD in only a few situations: when you ascend, when you descend, moving from one depth to another and inflating when you are on the surface.
Your buoyancy is closely related to the amount of weights that you use. Sometimes people think that to be over weighted is always better as it helps you to get down easier. This argument sounds logical but it is not always true. When you are over weighted the weight tends to drag the lower part of your body down. To compensate for this you need to put more air into your BCD to obtain a neutrally buoyant position, pulling your torso up. Although you might achieve a state of being ‘weightless in the water’, the position of your body is no longer streamlined. Instead of moving through the water in a horizontal position with a small impact area (your head and shoulders), you now push through the water with your entire body. This then leads to the opposite of the desired effect as you end up using much more energy to move which leads to you consuming a lot more air during your dive.
We seldom use our full lunge capacity when we are on the surface. Practicing meditation and yoga teaches us to breathe deeper and more slowly. A similar breathing pattern should be followed when diving. Slow and deep and continuous. This slows down your mind and your movements and helps you to conserve air. It also helps with your buoyancy. When you breathe in deeply and fill your lunges to their full capacity, you will feel that your body becomes lighter, and that you go up slowly in the water without needing to move your fins or arms. If you then breathe out you move down.
Normal breathing, like we are used to on the surface, is not enough to create this effect. You need to breathe deep enough so that your lunges expand and create an air pocket similar to a fish’s swim bladder. You thus need to breathe as deeply as you can to feel the effect best. When you want to go down, making use of breath control you need to exhale all the air in your lounges, something we very seldom do on land.
Factors affecting buoyancy
Body weight: Larger bodies (due to either muscle or fat tissue) require more weights.
Wet suit: The amount of weight that you need depends on your exposure suit. Thicker and newer suits require more weights. Neoprene is injected with micro air bubbles. Thicker suits have more of these bubbles, making you more buoyant. The bubbles in newer suits are larger as they had not been exposed to the pressure that could compress and make these bubbles smaller over time.
Dive site/water: Diving in different sites could affect your buoyancy. Fresh water environments require fewer weights than salt water. The salt particles in the water makes each litre heavier, thus you need to displace more water to become neutrally buoyant. You achieve this by adding more weights.
Depth: As you go deeper two things happen to affect your buoyancy. Firstly the pressure causes the micro bubbles in your exposure suit to compress, making the suit, and you, less buoyant. Secondly the air in your BCD compresses under the pressure, requiring you to add more air to become neutrally buoyant at depth. When you return to a shallower depth you would need to remove some air again to compensate for the expansion of the air
Experience: buoyancy is not an exact science. No one can tell you exactly how much air to put in your BCD to make you neutrally buoyant. It is very much a feeling and one that you develop by diving more often and gaining more experience in the magical underwater realm.
* A version of this article first appeared at www.scubadiverlife.com