Diving Without a BCD

by Sean Harrison, VP of Training

BCDAs article topics were being discussed, diving without a BCD (buoyancy control device) caught my attention and I jumped right on it. I did this for a few reasons. Over the years I have dived with many different BCDs, and in some cases without a BCD. I have also seen and heard of divers diving without a BCD (for the wrong reasons) and using the wrong BCD for the dive they had planned.

Let’s look at what not to do or use for a BCD. Often divers will get very comfortable with a BCD, and rightfully so. A good BCD should fit perfect, feel comfortable and the diver should know where every pocket and clip is, but one BCD may not be right for all types of dives.

Divers buying their first set of gear will choose equipment that is suited for the dives they have always wanted to do or for the trip they have planned, and often times this means warm tropical dives. For these types of dives, focusing on the BCD of course, the best BCD is one that provides appropriate lift for minimal thermal protect and features a single cylinder attachment. The BCD may also be very streamlined and have D-Rings made of plastic that are located in areas where lights and slates or even a camera may be attached. While this type of BCD is well suited for these dives, it will not work for colder dives, which require a lot more weight for the diver to submerge, or for technical dives, where the diver will be carrying additional cylinders. Technical BCD’s typically have metal D-Rings that are adjustable and are located differently so that stage bottles can be clipped in the correct location. Technical BCD’s also will have interchangeable air cells so the lift capacity can be increased or decreased based on what the diver is carrying. Finally, these BCDs also have the capability of attaching to a rebreather, if the rebreather is designed to be used with the diver’s BCD.

The final item on the ‘what not to do’ list is use other forms of trapped air as a buoyancy device. Divers have been known to use their drysuits as a primary buoyancy device. This is not only an unsafe practice, it also goes against most manufacturers’ recommendations (check owner’s manual for specific recommendations on how to use drysuit). In theory, this sounds like it would work, the diver is controlling one air space, the drysuit, rather than two, the drysuit and BCD, but it just does not work out that way. The unsafe aspect of using a drysuit as a ‘BCD’ is that the suit has seals to keep the air in, should a diver change his attitude to be vertical to make an ascent, the neck seal would vent excess air, decreasing the lift capacity and causing the diver to descend or swim harder to continue to ascend. This cycle would keep repeating itself, as the air expands during ascent.

Now for the slightly more sensitive subject of no BCD, this is really only practiced in commercial diving application where divers are tethered (connected by a line to a tender on the surface) to the surface and the surface support staff control their descent and ascent, sometimes by pulling on the diver or by raising and lowering a platform. These divers have no need to achieve neutral buoyancy and the additional air cell would only get in the way and may be punctured by sharp objects. Sport and technical divers should never consider diving without a BCD that has an air cell.

A BCD is just like any other ‘tool for the job’ in that you should pick the right BCD for the dive you are planning. There are simple solutions and BCDs that will work for multiple types of dives by simply changing out the air cell (adjusting lift capacity). This option allows the diver to get comfortable with one harness system and build the muscle memory of where his inflator, cutting device, lights and safety equipment are attached. The best thing to remember is to use the right BCD and don’t just use what you have, or you may find yourself in a sticky situation.

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4 Responses to Diving Without a BCD

  1. Jeff Frank says:

    Having recently gone through drysuit training, I find it odd that the recommendation in this article goes against what I was taught… to use the BCD only for attaining positive buoyancy on the surface while using the drysuit for buoyancy during the dive. The author states that air would vent through the neck seal, but that seems unlikely given that drysuits use vent valves, usually on the left shoulder, that would vent air long before popping the neck seal. I think some clarity is in order.

    • dpace says:

      Jeff, Thank you for reading the article and giving your feedback. The practice of using a drysuit as a BCD has been around for a long time so it does not surprise me that you would be taught that during a course however, as I said in the article there are some concerns worth considering before doing that.
      The only drysuit company I can quote off the top of my head that has a good recommendation or guideline for how much air should be in your suit (if properly weighted) is DUI. DUI says that if you were to raise one arm while submerged that the air bubble in that arm should go from the wrist to the elbow. I am sure other drysuit manufactures have similar such guidelines I just don’t know them. Another way of measuring the proper air to put in a drysuit is to only add enough to relieve a pinch or squeeze, this is of course done when the diver is in a prone or horizontal position.
      Now for the air venting through the neck seal. If you have excessive air in your suit and you go in a vertical position, head up feet down, the neck seal is the highest part of the suit. The exhaust valve, if the suit is equipped with a shoulder vent and not a wrist vent, would be roughly six to eight inches lower. Most shoulder vents are closer to the upper bicep as opposed to right on the shoulder where they would interfere with the BCD shoulder strap. One final point on this is, if your neck seal is so tight it holds back a large amount of air, you may want to consider trimming it back a little. Neck seals that are too tight reduce blood flow through the carotid arteries and can cause some major problems while diving.
      I hope I have clarified this a little for you and that you are enjoying using your drysuit. I am an avid drysuit diver and enjoy using mine every time I get in the water. As a final note, consult your drysuit user manual and see what their recommendations are, nobody knows how the equipment will perform better than the person that made it.

      Safe diving

  2. haydn leaker says:

    Frankly I am shocked at your comment that using a drysuit as a primary buouyancy device is an unsafe practice. I believe most dry suit divers do exactly this – do you agree? What evidence of any issues do you have to back up your unsafe assertion? I use an Otter Drysuit, with cuff dump, and have done so for 18 years, and there is no comment about this in their instruction manual – what manufacturers say you should not follow this practice?

  3. Joey says:

    I have dove with no bc for some time both with 7 mil wetsuits and dry suits . I have found that when weighted properly I can be neutral without one by using my own internal bc often called “lungs”.

    I see little to no point in using a bc unless its to hold your tank. Or possibly as a surface flotation device .
    By weighting one selfs properly and planning your dive and diving your plan there is no need for a bc I can be positive on the surface hold a safety stop and be neutral at depth

  4. I have used my drysuit as a bouyancy device as weel. Yes I know its not the greatest prctice, but if you know what you are doing it works.

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