Buoyancy Compensator (BCD) Styles and Features

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Inflation Style

Cressi Start and Aqualung Libra Buoyancy Compensators
Buoyancy Compensator Styles and Features This photo shows examples of two different styles of buoyancy compensators. The Cressi Start (left) is a vest-style buoyancy compensator, while the Aqualung Libra (right) is a back-inflating buoyancy compensator. Images reproduced with the permission of Cressi and Aqualung.

A buoyancy compensator (also known as a buoyancy control device, BCD, or BC) has two basic functions in scuba diving. It allows a diver to control his buoyancy, and therefore his depth, during a dive, and it attaches the tank to the diver.

While all buoyancy compensators share these common functions, they accomplish the functions in a startling variety of ways. From the differences between vest-style and back-inflating buoyancy compensators, to the various kinds of accessory pockets, scuba divers should have a clear understanding of the different styles of BCs before purchase. Here are twelve common features of BCs to consider.

One important consideration when choosing a buoyancy compensator (BC) is the style of inflation. Divers can choose between vest-style BCs and back-inflating BCs, both of which have advantages and disadvantages.

Vest-style buoyancy compensators are commonly used as rental gear, and most divers learn to dive using a vest-style BC. Generally, divers are already familiar with vest-style BCs, and will find them intuitive and easy to use. A vest-style BC floats a diver easily with his head out of the water, but may squeeze his chest uncomfortably when fully inflated.

Back-inflating buoyancy compensators are becoming common in recreational diving. Because they do not inflate around a diver's sides and chest, many divers find back-inflating BCs very comfortable. These BCs tend to put divers in the ideal horizontal swimming position. While very comfortable to use, back-inflating BCs may take a little time to learn to use properly.

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Photos of the Cressi Back Jac and Cressi Aqua Pro 5
Buoyancy Compensator Styles and Features The Cressi Back Jac buoyancy compensator has more lift than a similarly-sized Cressi Aqua Pro 5. Images reproduced with the permission of Cressi.

The most fundamental characteristic of a buoyancy compensator (BC) is the amount of lift it provides. A BC's lift is usually given in pounds or kilograms. For example, a BC with 27 pounds of lift will increase a diver's positive buoyancy by 27 pounds when fully inflated.

When choosing a buoyancy compensator, a diver should consider how much lift he will need. The goal is to choose a BC that can comfortably float a diver on the surface when partially full. A diver using a BC with too little lift will have a hard time floating on the surface, and may have to kick to keep his head above the water. A diver using a BC with excessive lift will have to drag a larger volume through the water than is necessary, which will increase drag even when the BC is not full. Different sizes of the same BC model usually have different amounts of lift.

Children and smaller divers will generally need less lift than larger divers. Divers who use more buoyant, aluminum tanks will need less lift than divers who use less buoyant, steel tanks. Exposure protection, such as a wetsuit or a drysuit, will also effect a diver's buoyancy and therefore the amount of lift he requires. Typically, the more weight a diver has to carry, the more lift he is likely to need. Finally, dive guides and instructors require BCs with greater lift than recreational divers, because they frequently carry extra weight for clients and assist clients with weights on the surface.

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Integrated Weight Systems

Photos of the Cressi Aqua Pro 5, Oceanic Aeris and ScubaPro Equator Buoyancy Compensators.
Buoyancy Compensator Styles and Features This photo shows examples integrated weight systems in buoyancy compensators: the Cressi AquaPro 5 (left), the Oceanic Aeris Atmos LX (top right), and the ScubaPro Equator (bottom right). Images reproduced with the permission of Cressi, Oceanic, and ScubaPro.

Integrated weight pockets eliminate the need for a diver to wear a weight belt. As many divers find that weight belts either press uncomfortably on their hips or tend to slide off, integrated weight pockets have come as a welcome innovation.

Integrated weight pockets are incorporated into buoyancy compensators in a variety of ways. Some hold loose weights, such as the Cressi Aqua Pro 5 on the left. Other BCs use removable pouches to hold weights. Once the weights are closed into a pouch, the entire pouch slides and locks into the BC.

Integrated weight systems come in a variety of styles, and most work very well. The most important consideration for a buoyancy compensator with an integrated weight system is that it allows for the quick release of the weights. A diver should be able to easily release the weights from the BC with one hand, which will make him float in the case of an emergency. The BCs above use a clip release for their integrated weight systems. When the clip is pressed, the weights will either fall free on their own (left) or can be pulled from the pocket and dropped (right). Divers new to buoyancy compensators with integrated weights should practice ditching the weights on the surface of before diving with them.

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Trim Weight Pockets

Photos of the Cressi Aqua Ride and Aqualung Zuma Buoyancy Compensators
Buoyancy Compensator Styles and Features Two examples of buoyancy compensators with trim weight pockets: the Cressi Aqua Ride (left) and the Aqualung Zuma (right). The trim weight pockets are circled in yellow. Images reproduced with the permission of Cressi and Aqualung.

Trim weight pockets allow a diver to distribute small amounts of weight to different areas of his buoyancy compensator (BC), which helps to adjust his balance and swimming position. For example, a diver who moves a few pounds of weight into upper shoulder trim weight pockets will have more head-down position than he did without the weights present. Trim weight pockets are generally located on a BC's upper back, shoulders, or tank bands.

Trim weight pockets do not allow for a quick release of weights in an emergency. Divers generally distribute only a few pounds of their weight into trim weight pockets, and leave the majority of their weight on a weight belt or in an integrated weight system. For example, a diver who normally uses sixteen pounds of weight may put four pounds into his buoyancy compensator's trim weight pockets, and leave the remaining twelve pounds on his weight belt. In an emergency, releasing the belt and its twelve pounds will still cause the diver to float.

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Dump Valves

Buoyancy Compensator Styles and Features The Cressi In Line BC (left) has several different dump valves, allowing it to be deflated from any position. This image shows close-ups of a standard Cressi dump valve (top right) and Aqualung's Signature Flat Valve (bottom left), which lies flat against the BC and decreases bulk. Images reproduced with the permission of Cressi and Aqualung

Dump valves allow a diver to quickly release air from a buoyancy compensator (BC). Four standard locations for BC dump valves exist: the right shoulder, the right and left lower portions of the BC, and the inflator pull dump. Divers may also release air from the BC using the deflate button on the inflator hose, but this is not considered a dump, and is standard on all BCs.

Buoyancy compensators have dump valves in various locations to allow a diver to release air from the BC without changing his position in the water. A diver who is in a vertical position can use the right shoulder dump to vent air from the BC. A diver in a horizontal, swimming position can use a lower dump to deflate his BC. The inflator hose pull dump is operated by pulling on the BC's inflator hose, which opens a valve on the BC's left shoulder. This dump requires that the diver be in a vertical position.

When considering a buoyancy compensator, a diver should check to see that it has at least one lower dump valve. This will allow the diver to deflate the BC in a horizontal position, which he can not do with the deflate button located on the inflator hose.

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Integrated Alternate Air Source

Photos of Integrated Alternate Air Source Regulators for Buoyancy Compensators
Buoyancy Compensator Styles and Features The ScubaPro Light Hawk (left) is an example of a buoyancy compensator that can be used with an integrated alternate air source. The Aqualung AirSource 3 (middle) and the Aqualung AirSource 2 (right) are integrated alternate air sources available on Aqualung BCs. Images reproduced with the permission of Scubapro and Aqualung.

An integrated alternate air source is an alternate second stage regulator incorporated into the buoyancy compensator's (BC's) inflator hose. Integrated alternate air sources eliminate the need for a diver to have a separate back-up regulator, or octopus, attached to his regulator first stage. Some models of integrated alternate air sources can reduce dive equipment's weight and bulk.

Divers new to integrated alternate air sources will need learn to use them properly. Emergency air sharing protocol changes when a diver switches to an integrated air source, as does the method for orally inflating the buoyancy compensator. In an emergency air sharing situation, a diver must remove his primary regulator and donate it to the out-of-air diver while switching to the integrated alternate air source. This can be tricky at first and requires practice.

Integrated alternate air sources attach to the regulator first stage via a non-standard hose connection. Usually, integrated alternate air sources are sold with a hose with the proper connection. However, divers should realize that once a regulator and BC have been adapted for use with an integrated alternate air source, they can no longer be used with standard scuba regulators and BCs. If the BC, the integrated alternate air source, or the regulator malfunction, it is likely the entire set of gear will need to be swapped out until the malfunctioning piece is fixed.

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D Rings

ScubaPro Geo and Cressi Aqua Ride Lady Buoyancy Compensators
Buoyancy Compensator Styles and Features The ScubaPro Geo and Cressi Aqua Ride Lady buoyancy compensators both have d-rings on the upper and lower areas of the BC. Images reproduced with the permission of ScubaPro and Cressi

Most buoyancy compensators (BCs) come with d-shaped metal or plastic rings that are used to attach dive accessories to the BC. Chest and waist straps may also have d-rings sewn into their ends to facilitate tightening the strap. Strap d-rings are not ideal for accessory attachment because the accessories will dangle below the diver and may damage coral or other delicate aquatic life.

When choosing a buoyancy compensator, a diver should consider whether the d-rings are easy to reach and convenient for accessory attachment. A BC should have d-rings on the shoulder or chest area and on the lower potion near the BC waist band or pockets, but ideal d-ring placement will vary from diver to diver. A diver should consider how and where he will attach his submersible pressure gauge and alternate second stage regulator to the buoyancy compensator.

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Light Weight and Easy to Pack

Photos of the ScubaPro Geo, Cressi Flex in the Sea, and Aqualung Zuma Buoyancy Compensators
Buoyancy Compensator Styles and Features The ScubaPro Geo (top right), Cressi Flex in the Sea (top left), and Aqualung Zuma (bottom) are light weight, travel-friendly buoyancy compensators which fold or roll up for easy packing. Images reproduced with the permission of ScubaPro, Cressi, and Aqualung

A buoyancy compensator (BC) is the bulkiest, and sometimes the heaviest piece of a diver's equipment. In light of contemporary airline baggage limits, a BC's weight has become a serious consideration for traveling divers. Dive equipment manufacturers have come up with a variety of clever ways to reduce a BC's weight and bulk to make it more efficient for packing and traveling. The buoyancy compensators above are all specifically designed for travel, and fold or roll into a very small space.

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Back Plate and Wing

Hollis Wing and Back Plate
Buoyancy Compensator Styles and Features A back plate and wing are layered together to create a very adaptable buoyancy compensator (BC). The back plate (left) is placed on top of the wings (middle) forming the buoyancy compensator (right). Hollis Elite E1 Harness and Backplate and the Hollis C Series Double Donut Wing by Oceanic.

Frequently seen in technical diving, the backplate and wing style of buoyancy compensator (BC) is becoming more common among recreational divers. This BC consists of two parts: the back plate, which is a hard metal plate with webbing harness, and the wing, the portion of the BC that inflates and deflates. The wing are completely independent of the backplate, and inflate behind the diver's back, making this a back inflating buoyancy compensator.

The advantage of a back plate and wing combination is that it is very adaptable. A back plate and wing can be used directly on double tanks, or attached to a single tank via a single tank adaptor. The wing can be switched out for models with more or less lift depending upon the equipment to be used on an dive. Recreational divers who are considering pursuing technical diving in the future would be well advised to purchase a back plate and wing combination, as it can be adapted to any future needs.

Back plate and wing buoyancy compensators are generally heavier and less buoyant than standard BCs. This can greatly reduce the weight required for a dive, and may make a back plate and wing combination preferable for divers who use buoyant exposure protection such as drysuits or thick wetsuits.

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Accessory Pockets

ScubaPro and Aqualung Buoyancy Compensator Pockets
Buoyancy Compensator Styles and Features Accessory pockets come in a variety of styles. The pockets in the ScubaPro Geo buoyancy compensator (upper left) close with a zipper, while those of the ScubaPro Pilot (bottom left) have a Velcro closure. The accessory pockets on the ScubaPro Light Hawk (middle) snap shut, while the Aqualung Pearl i3 (right) has a drop down pocket that can be stowed when not in use. Images reproduced with the permission of ScubaPro and Aqualung

Accessory pockets are designed to hold a variety of diving tools, such a reels, spools, slates, and back-up masks. A diver should take into account what dive accessories he is likely to use, and check that the buoyancy compensator he is considering has appropriately sized pockets. In general, the bigger the pocket, the better.

Buoyancy compensator accessory pockets may close with Velcro, zippers, or even clips. Although zippers may be difficult to manipulate, they tend to stay closed during a dive while Velcro closures have been known to flap open as divers enter the water, especially when there is a heavy object in the pocket. On the other hand, Velcro is less likely to break or jam.

Some buoyancy compensators have drop down or expandable pockets that can be stowed when not in use, such as the pocket on the Aqualung Pearl i3 (right). The Aqualung Pearl i3 also features a standard knife mount for the attachment of a dive knife.

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Chest Straps

Buoyancy Compensator Styles and Features The Aqualung Zuma (left) and the Cressi Light Jac (right) are two examples of buoyancy compensators with chest straps. The Aqualung Zuma features an adjustable height chest strap which may help to keep the chest strap from riding uncomfortably high on a diver's neck. Images reproduced with the permission of Aqualung and Cressi.

Chest straps are standard on most contemporary buoyancy compensators (BCs), although it is still possible to find models without chest straps. Chest straps keep the BC from sliding off over a divers shoulders. Scuba divers with thin shoulders may find chest straps a useful feature, while those with wider shoulders may find them unnecessary.

Many divers complain that chest straps slide up against the base of their necks and choke them. This usually happens entering or exiting the water, when the full weight of the tank is pulling down on the buoyancy compensator. To address this problem, some dive equipment manufacturers, such as Aqualung, have developed adjustable-height chest straps, which can be lowered so as to not press on the neck.

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Women's Styles

Buoyancy Compensator Styles and Features The Aqualung Pearl i3 and Cressi Lady Jac buoyancy compensators are designed specifically for female divers. Images reproduced with the permission of Aqualung and Cressi.

Yes, sometimes buoyancy compensators for women come in pink and purple, but color is not the main difference between a standard buoyancy compensator (BC) and one designed specifically for a woman.

Buoyancy compensators designed for women are cut to fit women's smaller frames. Many feature bodice-like closures, such as the Aqualung Pearl i3, which keep the BC from sliding off a diver's shoulders without the need for a potentially uncomfortable chest strap.

Women's buoyancy compensators may also have less lift than standard BCs to accommodate for women's smaller sizes.