Buoyancy Compensator Device (BCD)
BCD (Buoyancy Compensator Device), often called BC (Buoyancy Compensator) is just like a jacket. A BC’s role in scuba diving is to maintain proper buoyancy for the diver. This is both for safety and comfort.
Diver attaches the dive tank to the BC. By the help of a hose, tank and the BC is interconnected. The working principle of BC is just like the sub-marines.
Sub-marines pump water to their water tanks to start to descent. Ofcourse they don’t want to hit the bottom/descent that deep in the ocean. So they leave a little bit of air inside their water tanks to go straight without sinking. When they want to surface, they pump out the water inside the water tanks and start to ascent.
Divers on the surface deflate their buoyancy compensators to start descending. To be able to “hover” at the depth the diver wants to, there has to be a perfect amount of air inside the BC. This is something both learned (from specialties like Perfect Buoyancy) and experienced. When divers want to ascent a little bit, they inflate their BC a little bit and raise to the desired position.
If I sum up, Buoyancy Compensator (BC) is used for neutral buoyancy and balance issues underwater.
In addition to this, divers fully inflate their BCs on the surface when they need to wait for their buddies, dive leader and etc. This way, they can easily become positively buoyant (float) and wait on the surface as long as they want to without any swimming aids.
Types of Buoyancy Compensators
There are 5 different types of buoyancy compensator devices. If you are a beginner I advise you to buy a Jacket Style BCD, which is easy to use and very common in recreational diving. Also it is easier to learn the fundamentals of a BC with it. If you have any questions about types of BC, please let me know by writing a comment below.
A very common BCD getting used all over the world. It is just like a jacket. There are lot of variations of jacket style BCDs, but the style is the same. Air bladder wrap divers from front, back and both sides.
A homogeneous air delivery is on the nail.
I always suggest my Open Water Diver students and any beginner divers to start their BCD journey by buying a Jacket Style BCD. Because it makes the diver stay in vertical position, which a person is used to.
In addition, diver feels the BCD on every side which psychologically relaxes the diver.
This type of BCs have pockets to store anything. If it is a weight-integrated Jacket Style BCD, it also has purses on both sides for housing weights. By this way, you are not using a separate weight belt.
Generally preferred by underwater photographers, Back-Inflated BCs’ air bladder is only located on the back. When you push the inflator, front or side parts don’t inflate, but the back.
With a back-inflate BCD, divers can stay in horizontal position easier than the Jacket Style BCD. Diver’s fron is uncluttered, so it is easy for the diver to hold an underwater camera, a strobe and etc in the front. That’s why this type of BCDs are better for underwater photographers.
A blend of Jacket Style and Back-Inflate BCD. Divers have more free space in the front like a Back-Inflate BCD. On the other hand, because Hybrid BCDs store the majority of the air on the back, it is still more comfortable in horizontal position.
Hybrid BCDs have been invented as an answer to “a buoyancy compensator inbetween” demand from the divers. Some divers don’t like few things with Back-Inflate BCDs. Forexample, when divers are on the surface, an inflated Back-Inflate BCD makes it harder to stay vertical on the surface. Divers should tilt their bodies back and stay on the BCD, laying backwards.
Some divers, on the other hand, don’t like few things with Jacket-Style BCDs. What I also experience with Jacket-Style BCD is that it forces most divers to fins down (close to vertical) position.
Hybrid BCDs are born as a mixture.
Just like Lego, Black Plate and Wing BCD is modular. There is a plate (generally made of stainless steel) on the back of the diver. There is no weight integration in this type, so using a stainless steel back plate instead of an anodised aluminium is a better option.
This way, divers can replace some weight in the belt using the negative buoyancy of the steel back plate. Generally, stainless steel is even enough especially in dives with steel dive tank. So the diver doesn’t require any other kind of weight.
Back Plate and Wing BCDs can be modified depending on the divers’ needs. One of the best advantage is that the parts can be replaced easily when needed.
You are designing your own BCD. Buy the harness, wing and back plate parts of your choice and bring them together to create your set!
BP & W BCD is mostly preferred by technical deep, cave and wreck divers. You can attach two dive tanks to this type of BC.
In terms of buoyancy, BP & W is really good. Because the gravity and the buoyancy centers are almost at the same point.
Especially used in narrow cave dives, Sidemount BCDs give the divers ability to carry the dive tanks on both sides, not the back. Divers carry the dive tanks under their arms.
Very useful especially for technical divers carrying two tanks at their backs and try to get into a tight cave entrance.
I have some suggestions before buying a BCD:
- If you are a beginner, start by buying a Jacket Style BCD. It is simple, no mounting needed and makes you perfectly vertical on the surface.
- Buy the BCD that fits you. If it is too small, you’ll loose air trying to sustain you neutral buoyancy. If it is too large, it will discomfort you, make you unbalanced even have the risk of getting out of you.
- If you are experienced and planning some technical diving, Back Plate & Wing or Sidemount BCD should be considered.