BCD stands for buoyancy compensating device. This is what you wear during dives to help you float at both the surface and deep in the water.
Have you ever stopped to wonder how the jacket you put on before a dive actually functions? How is it possible that this floating device still lets you swim down to deep waters, for example?
Or maybe you are an experienced diver and looking for a different kind of BCD to add to your scuba diving gear because you want to change your type of dives. There is a wide variety of BCDs available, each one more suitable for a different dive style.
How Does a BCD Work and Why Do We Need One?
Whatever your reason, it helps to know how a BCD works exactly. Here is a quick overview of the workings of a buoyancy compensating device and why us divers need to use one underwater.
What Is Buoyancy?
Having control over your BCD allows you to swim down to deeper depths, stay at a specific level and float to the surface. In other words, it gives you control over your buoyancy as the name suggests.
To understand how a BCD works you need to understand the concept of buoyancy. Basically, buoyancy is the balance between two opposite forces – in this case, the upward force of the water versus the downward force of your weight and gear.
Being buoyant means that you float, either at a certain level underwater or at the surface because the upward force is greater than the downward force. Being negatively buoyant means that you sink because the downward force is greater than the upward force.
How much air is inside your BCD in combination with your body weight and gear weight determines how buoyant you are.
Inflating the BCD increases the upward force causing you to rise in the water while deflating the BCD increases the downward force and lets you dive deeper.
Why do You Need a BCD?
So why do you need a BCD during a dive? A BCD gives you control over how deep or shallow you want to be in the water. It lets you dive down into the water easier, float at specific depths and rise to the surface. This is important for a few reasons. The first reason is a safety precaution; controlling your decompression rate.
The second reason is not only for safety but also for comfort. Good control over a BCD lets you stay at specific depths with minimal effort. In other words, you can stay at the same depth while simply floating. Also, you can dive deeper and rise up with less effort in your swimming.
That’s why it’s always a good idea to learn how to perfect your buoyancy control and practice these skills on a regular basis.
How to Control Your Buoyancy with a BCD
When you are learning to dive, your instructor makes you practice changing your buoyancy using the BCD. This is an essential skill in diving because it keeps you in control of the dive.
This is how a BCD works. The BCD is connected to the pressurized air tank so that you can wear it on your back. When you are in the water your goal is to dive deeper meaning that you need to make yourself less buoyant. You do this by releasing the air inside the BCD in small amounts.
Gradually release the air because your descent should be slow. Releasing too much air too fast makes sink down rather than dive down.
There is also a connection between the BCD and the first stage of the air tank. This lets you add air directly to the BCD using the air-inflation valve.
Adding air increases the upward force meaning that you will float. Again, add air in small amounts at a time for a more controlled float.
You are also likely to use the BCD to stay at a certain level in the water, for example at 15 meters below the surface. Adding too much air makes you lose control over the dive.
Rapidly increasing your buoyancy sends you towards the surface too fast. As any diver knows, this is dangerous because you also need control over your decompression.
Different Types of BCD
There are different kinds of BCDs; back flotation BCD, weight-integrated BCD, and lighter travel BCDs. Depending on what kind of diver you are, one of these BCDs might work better for you.
The most common BCD type is the back flotation BCD which puts weight between your back and the pressurized air tank. Because of the design of this BCD, it is harder to float involuntarily.
A weight-integrated BCD has weights in designated pockets which the diver can release at any time. This replaces the weight belt.
A travel BCD is basically a lighter version of other BCD types. This BCD type is less dense so that it is easier to carry inside travel bags.