Commonly referred to as BCD (Buoyancy Compensating Device) or BC (Buoyancy Compensator) or Stab (Stabilising) Jacket, the modern BCD allows the accurate addition and subtraction of air whilst in the water to adjust buoyancy.
An extremely muscular and athletic person might naturally sink in water, even without any scuba gear on at all. Put that person in a BCD without any air in it, and he or she will probably still sink. But add a bit of air to that BCD, and that entire unit — the person and the equipment — becomes marginally larger, without any appreciable increase in weight. In very short order, the diver weighs less than the volume of water that he or she is displacing. As soon as that happens, they float! That is, they become positively buoyant. If the BCD is inflated so that the diver weighs the same as the water they are displacing, they become neutrally buoyant, which is what divers want to be most of the time.
BCDs become even more important when divers use neoprene wetsuits, which are buoyant at the surface. As divers go deeper, the little nitrogen-filled cells in the neoprene foam are pressed smaller and smaller by the water pressure, and the suit becomes less buoyant. So a suit that may have required the diver to add 10 kg (20 lb) of lead weight at the surface in order to submerge will probably not have enough 'float' to keep the diver from sinking once he or she is 10 or 20 metres underwater. Add a touch of air from the scuba tank (there is a special hose and a button on the BCD that lets you do this) and the ability to hover is regained. When the diver goes up, he or she releases air to offset the extra buoyancy as the wetsuit cells expand again. Many BCDs have more than one means of doing this.
A good BCD does more than just keep you off the bottom. It also allows you to maintain depth without kicking, and lets you swim in a horizontal, rather than angled, position. Less kicking means less energy required, and less air consumed. And swimming horizontally helps you stay as streamlined as possible — which again consumes less energy and less air. So a good BCD, used well, can literally mean the difference between a 20 minute dive and a one hour dive.
There's another benefit. When the diver gets back to the surface, the BCD can be inflated to keep the diver relaxed and afloat while working back to the boat or the shore. And the BCD can assist at the surface in carrying stuff you might find or catch while diving. With this in mind, you will often hear discussions of how much 'lift' a particular BCD has. This is a reference to how much weight it can support when fully inflated.
While the old adage, 'you get what you pay for' is true in most things in life, it's worth noting that price is not necessarily an indicator of the level of diving for which a BCD is intended. Deep, technical shipwreck divers often opt for a BC design that is one of the simplest — and therefore can cost less than some designs used for general recreational diving.
As with most dive gear, different types of BCDs are preferred for different types of diving. A weight- and space-conscious traveling diver may be willing to go without some features in order to have a BC that folds and packs compactly and adds little to the weight of a gear bag.
A diver using tools such as line reels and work slates during a dive may want a BCD that puts most of the flotation in back, between the diver and the tank, and leaves the front of the BC open for attaching those tools.
A diving instructor who spends much of her day floating at the surface and talking with her class may prefer a BCD that moves some of that flotation to the front, so she can effortlessly float upright on the surface between dives.
And divers wearing drysuits (to which air is also added during a dive) will look for BCD styles that work harmoniously with the drysuit's design, and the buoyancy provided by the suit.
All BCDs must do two things. When fully inflated, they must be capable of comfortably floating the diver, with all of his or her gear for the dive at hand, at the surface, with no other assistance. And they must fit well, with all releases and controls easy to reach. Beyond that, it's simply a matter of matching the BCD to the diving you want to do.
The first BCDs designed for recreational divers were based fairly closely on the inflatable personal flotation devices used by pilots and military aircrews. These were later refined into what was known as a Horse Collar BCD, which placed most of the flotation on the diverís chest and behind the diverís neck. The good news was that this tended to float the diver face-up — a desirable attribute if an exhausted or injured diver had to be taken to the surface. The bad news was that this sort of BCD also tended to roll the diver face-up under water. Learning how to ride the bubble of buoyancy on one's chest was a skill easily acquired, but it was not effortless. So gear designers began looking for a different approach.
In the 1970s, they came up with the Jacket Style BCD, also known in some regions as a stabilising jacket or stab jacket: a BCD in which the cells providing the buoyancy completely surrounded the diver's torso. This made it possible for the diver to still float upright at the surface, but it made swimming underwater a much more intuitive process. Because of this win/win approach, jacket-style BCDs quickly became, and still remain, the most popular style of BCDs with general recreational scuba divers.
A style of BCD that makes hovering horizontally almost completely effortless is the Back or Rear Inflation BCD. In this design, the BCD's air bladder is worn on a harness and sandwiched between the diver and his or her tanks. Because such a BCD allows you to 'trim out' horizontally so easily, it tends to be very popular with divers who operate in confined spaces, such as shipwrecks or caverns and caves. Also, because this type of BC does not squeeze in on the diver as it is inflated, it tends to work really well with drysuits, which must have room for air movement in order to work optimally. Since this type of BCD doesn't necessarily float an unconscious diver face-up at the surface, it tends to be used more by experienced divers who are experienced in distributing the weight of their equipment.
Both of these basic types of BCDs are available as Travel BCDs, which are designed to fold and store more compactly than conventional BCs.
Both are often available in weight integrated forms, which sometimes do away with the need to wear a weight belt to offset the natural buoyancy of most wetsuits and drysuits. With a weight-integrated BCD, the weight is carried in specially designed pockets that allow the diver to 'ditch' (or drop) the weights in an instant if necessary.
And as a reflection of the growing number of women diving, Women's BCDs are now available from many manufacturers. These are anatomically cut and styled to fit women more comfortably.
A number of other features and options are available on today's BCDs. On some, the low pressure inflator used to add air from the cylinder can also be used as a back-up regulator. Many newer BCDs incorporate features to help streamline the diver and reduce or eliminate dangling items of gear. And because image is important, even when you're underwater, some BCDs are available in colours (and even prints) designed to complement the rest of your gear.
Because the two pieces of gear work so closely together, most people buy their first BCD at the same time that they buy their first regulator set. This is why we offer Scuba Packages that combine a BCD with Regulators, Instruments and Dive Computer.
If you're pretty certain what sort of diving you're going to be doing, you might even purchase your BCD before you've started your Open Water Course, so you can practice with your own gear and get accustomed to it in the class. Or if you're still uncertain what sort of diving you most enjoy, you might want to discuss the options with us and then buy your BC.
Because fit is so important with a BCD, see if you can try the BC on with the wetsuit or drysuit that you will be wearing for your diving. If you're planning on using more than one suit, try the BCD on with the bulkiest suit you intend to dive in, and ask us to help you assess the fit. You want a BCD on which you can reach all the controls and releases easily, without stretching or straining.
If you have a scuba cylinder (tank) on when you try the BCD, it will probably hang a little low in back and pull the BCD back on your shoulders. Don't be concerned about this, because the cylinder and BC will ride in a much more natural position when you're in the water. In the store, how the BCD hangs without a tank is a much better indication of how it will ride when you're using it in the water.
To help you select the correct size BCD we have drawn up an approximate size chart – some BCDs have their own size chart as supplied by the manufacturers which supersedes this chart.
|Extra Extra Large||122-127||48-50|
This is only an approximate guide and you should always try your BCD as soon as you receive it and before actually using it to ensure the correct fit in case you find you need a different size.
The measurements shown are chest measurements over your exposure protection, so if for example you have 42 inch chest and wear a dry suit which is approximately 2 inches of bulk, you should consider a size compatible with a 44 inch chest.
Weight integration built into a BCD can mean you may not need to wear a weight belt. This takes the bulky lead off your waist and puts it into quick release pouches either side of the BCD. You still have the option to wear extra lead on a belt if you need it but integrated weights can't slip down your waist and are less likely to be forgotten than a belt. They're much easier to put on in the water too.
The only downside to integrated weights is that it makes your scuba unit heavy when carrying it around on the surface and getting it out of the water. You can always take the pouches out to make it lighter but most divers leave them in.
Generally, in warmer waters with no wetsuit or just a 3 mm wetsuit, you'll get all of the weight you need into the integrated weight pockets. However, in temperate and cold water with a 7 mm wetsuit or drysuit, you'll probably need a weight belt or harness as well.
Modern ladies BCDs offer female divers increased comfort and a much better fit compared to the unisex alternatives. Key features are that the back length is reduced, which means the cylinder does not rest on the base of your spine and the shape of the BCD is made to fit the female figure.
Integrated weights save ladies hips from the bruising sometimes suffered by using a conventional weight belt. Also, often the chest straps are removed on a ladies BCD to avoid constriction across the bust.
BCDs come in two basic shapes: Jackets and Wings. Most divers learn to dive using a jacket style BCD. These inflate all around your body and around your waist so you feel nice and secure in the water and you sit in a nice position on the surface. Wing BCDs only inflate behind you, typically in a donut shape or horseshoe shape between you and your cylinder. Wing's are preferred by more experienced divers because they hold you in a horizontal position in the water and do not obstruct your movements when fully inflated.
Wings are lighter and usually have greater adjustment in the straps with a simpler harness style strap system. Jacket BCDs typically have pockets built in either side of them for storage which makes them heavier for travel.
A lot is said regarding the lift capacity of a BCD, however lift of the BCD (i.e. the amount of negative weight the BCD can float) should not replace proper weighting and most recreational BCDs will hold a single 12 or 15 litre steel or aluminium cylinder.
As with all diving you should ensure you are correctly weighted before the dive so you shouldn't need to use your BCD too much.
You should always avoid being over weighted otherwise you waste a lot of gas adjusting your buoyancy when you change depth. With this in mind, all BCDs offer plenty of lift for single cylinders. The exceptions come when you start to carry multiple cylinders, or extra tools, which will increase your need for extra lift.
Tropical Diving (with little or no wet suit protection): 8 to 12 kg of lift is plenty.
Recreational Diving (with a full wet suit or dry suit): 10 to 20 kg of lift.
Technical Diving (or diving under other demanding conditions): 20 to 40 kg plus of left.
A unit which combines the BCD inflator with an alternate 2nd stage regulator (octopus) can replace the normal inflator/deflator mechanism on your BCD and still allow you to inflate and deflate in the standard way, but also gives you a built in spare second stage regulator.
These are usually only slightly bigger than the normal inflation units that are available. Using an alternate inflator regulator means that you do not have to have an octopus (secondary second stage) and in and out of air situation, you donate your primary second stage and breath off the alternate inflator regulator (you can still control your buoyancy even when it's in your mouth).
Some consider these systems ideal for travelling divers who wish to reduce the weight and bulk of equipment. However like all new equipment we would recommend practicing using yours in a controlled environment first with your buddy.
We don't like them for many reasons. Firstly, they use non-standard hoses and connections. So if a hose goes while you're away on a holiday and a hose goes, chances are you won't be able to replace it. There are workarounds for this, but few divers implement them. Also, you'll be trying to breath from the combined unit on your left side, plus still using it as an inflator. This takes a lot of getting used to. Plus your dive buddy will be on the primary 2nd stage, and it's hose length is a lot shorter than a standard octopus regulator hose, so he or she will be crowding you.
Travel BCDs are designed to minimise weight and bulk to make travelling with them easier.
They tend to be made of lower denier materials with only basic features and are most suitable for tropical locations. Thinner material makes them lighter but also more fragile. They can cope with plenty of dives, but too much rough and tumble around sharp rocks or wrecks can puncture the bladder so they're best for open water diving.
Often steel D-rings will be replaced by plastic or aluminium ones which are strong but much lighter to help reduce the weight of the BCD.
Dump valves are one-way over pressure valves to allow excess gas to escape when you're fully inflated and allow you to dump gas in the water to adjust your buoyancy. Usually located behind your right shoulder and near the kidneys, you'll have a small cord that you can pull to open the valve. Most BCDs have at least two so you can alter your buoyancy in any position.
Some modern BCDs have pull dump built into the inflator on the left shoulder by a small cable inside the corrugated hose so when you pull the inflator down in an upright position you will dump gas. You should learn where these are by feel so you can quickly and intuitively dump gas without looking.
Make sure that your BCD has enough pockets and D-rings for the kind of diving that you are planning to do most. Often D-rings are pre-bent over your shoulders to flare outwards towards the bottom which makes attaching clips much easier than with flat D-rings which tend to lay flat against the BCD or straight out, usually found around your waist.
In tropical waters, one or two small pockets will suffice. They are useful for carrying things like your Fish ID slate. For temperate and cold water diving, you will probably want to carry more equipment such as a dSMB and reel, or spare mask, but you can always use thigh pockets for extra storage.
BCD inflation can either come from the traditional over the left shoulder inflator/deflator hose or from “air trim” style inflators that are located lower down in a more natural hand position.
We have plenty of amazing scuba diving BCD options available for you to choose from, but the following are our favourites:
Mares Prime BCD with Integrated Weight System
RRP: $599, Our Price: $539, You Save $60 (10%).
While you can buy a wide range of traditional jacket BCDs with wrap around inflation bladders in our online store, our favourite is the Mares Prime BCD with Integrated Weight System. It's made rugged and durable to take the rigors of frequent diving, and is more feature packed than comparable jacket BCDs.
Cressi Travelight BCD, Blue
Our Price: $759
Scubalab Travel BCs Testers Choice. A full-featured jacket style buoyancy control device that is extremely lightweight, without sacrificing quality, finish and acessories, making it irreplaceable for the traveling diver.
Cressi Travelight Lady BCD, Pink
Our Price: $759
This female specific version of the Cressi Travelight BCD features a cut to better suit women, plus lilac coloured trim.
This top-of-the-line Cressi Commander Evolution BCD combines the very best of the recreational and technical BCD design features. With ample D-rings for clipping on accessories, and a high lift capacity rear inflation bladder for improved trim and control in the water, this BC is great for whatever recreational diving you may wish to do.
Mares XR-REC Silver Single Backmount Set
RRP: $1,399, Our Price: $1,259, You Save $140 (10%).
This one size fits all complete harness and wing style BCD ticks all of our boxes and will tick yours too! Because we believe this is a great solution not only for divers learning buoyancy control, but also for experienced divers who want better trim and stability in the water from their BCD.
These accessories will help you care for your BCD and keep you diving safely.
Underwater Kinetics Super BC and Regulator Hanger
RRP: $27.50, Our Price: $25, You Save $2.50 (9%).
This is the sturdy hanger you need to properly hang and dry your BCD. We use them in the dive shop for our scuba rental equipment, plus on our own personal BCDs.
Trident BCD Washout Hose
RRP: $86, Our Price: $77, You Save $9 (10%).
Rinsing your BCD Bladder is important to the life of your Buoyancy Control Device. Mineral deposits and salt crystals when allowed to dry can cut right through the Urethane Laminate or Bladder requiring replacement of the BCD bag or bladder. This unique design not only cleans your BCD Internal Bladder, but it also cleans your Inflator mechanism.
Adrenalin Wetsuit and Gear Wash Concentrate - 250ml
Our Price: $11
This stuff will keep your BCD smelling fresh and clean from salinity. It cleans, kills bacteria, deodorises and prolongs the life of your valuable BCD.
BCDs should be rinsed in clean, fresh water at the end of each day of diving, and the air bladder should be drained of any water that has entered it during the dive, and then well rinsed with clean, potable water as well. When you store a BCD, the interior of the air bladder should be dry, and you want to store it with enough air in the BC to keep the sides of the bladder from sticking to one another. For longest life it's best to store a BCD away from heat and ozone sources (such as furnaces and water heaters) and away from direct sunlight.
For more information about how to properly look after your BCD, please see Buoyancy Compensator Care.