What Happens when you Take your BCD off at Depth

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IncreaseMyT

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There are scenarios where this could possibly come into play, maybe your gear needs a quick adjustment that you cannot reach without taking it off. I have seen this happen in real time, when we were not practicing it. I looked for the video of it today but cannot find it.

The first thing that happens is you start to ascend and now you will become inverted, because you are hanging on to your BCD. This is because you are extremely positively buoyant with air in your lungs at depth. This is in contrast to free diving. I had the pleasure of someone from here on the board teaching me the basics of free diving last year.

When you are free diving you will need some weight. I personally need 6-8 pounds in saltwater. This sets my neutral buoyancy depth at about 15-20 feet. This is important because on your way back up your buddy diver will be diving down to your neutrally buoyant depth to watch your eyes as you ascend. Below this marker on the line, you become more and more negatively buoyant as you descend.

When you are at depth and take off your BCD you become really buoyant, because unlike the free diver your lungs did not collapse to the size of a plum. So you have this big balloon in your chest.

If someone is in an emergency buoyant ascent not having your BCD will make you go up to the top automatically, because you will have no weight (unless you are also wearing a weight belt) and the air in your lungs will expand as you go up, so if you blacked out you will still go to the surface, and the compressed air in your lungs would expand and make you breathe out automatically.

So, what do others do if they need to remove their BCD to offset this extreme positive buoyancy once your BCD has been removed? Because everyone is going to cork to the top without it, regardless of your body fat.
 
The first thing that happens is you start to ascend and now you will be inverted. This is because you are extremely positively buoyant with air in your lungs at depth.

I've removed my BCD several times at depth. I never became inverted. I guess I did it wrong.

So you have this big balloon in your chest.

I don't have a big balloon in my chest when I dive. I breathe in and out when I dive and the times I removed my BCD for practice, or to tighten the tank, or make some adjustment, I did not become very buoyant. Even though I was no longer wearing my BCD with integrated weights and a tank, which do contribute to negative buoyancy. In general, when a diver no longer wears his or her BCD they will tend to become positively buoyant more or less, depending on how much weight they were wearing in their integrated BCD.

So, what do others do if they need to remove their BCD to offset this extreme positive buoyancy once your BCD has been removed?

I hold onto it. It might be useful at some point during the rest of the dive.
 
It also depends on where you wear your weight. In addition to my BCs integrated weights, I often have some of the weight on a belt, so that I would be closer to neutral if I needed to get out of my BC.
 
when I dive and the times I removed my BCD I did not become very buoyant.
I guess that you dive wet.

I dive dry, with pretty heavy undergarments. Even if my belt is almost uncomfortably heavy, my rig is noticeably negative underwater. I wouldn't enjoy having to ditch underwater, because I'm pretty certain I'd be hanging vertically, feet up and head down, desperately clinging to my rig to avoid corking like a Polaris missile.
 
It also depends on where you wear your weight. In addition to my BCs integrated weights, I often have some of the weight on a belt, so that I would be closer to neutral if I needed to get out of my BC.

True, but if you ditched that you would be super positively buoyant correct?

I guess I should have put that all weight is on the rig. But you bring up a very good point, we are all running different rigs so it is individual specific. Like for instance, I run a big steel 133 so me dropping 4 pounds isn't going to do a ton. I also have most of my weight in the trim pockets.

Usually when I remove my BCD for the purposes of adjustment, I let all the air out of my BCD so it sits on the ground, unless I only have to take it halfway off or something. I also do this when drift diving, if I am drifting too fast I will let all the air out of my BCD and sit on the bottom in between coral or wrecks to let the group catch up, especially if it's a nice white sandy bottom.
 
Sitting on the bottom is extremely bad form.

Not its not. It's a great way to conserve energy when trying to get out of a drift. Just like its good form to swim on the other side of the wreck in a drift, not on the face of it.
 
Sitting on the bottom is extremely bad form.
If you're able to sit on the bottom, you're overweighted. Seriously so. Unless you're carrying a serious twinset and plan to breathe it down, and you're at the beginning of your dive.
 
If you're able to sit on the bottom, you're overweighted. Seriously so.

Speak for yourself man. My weight is perfect, I barely need any air in my BCD during a dive. But if I let all the air out of it, I can easily breathe down to the bottom and take a break. I do it all the time on drifts, I usually drift the fastest in the group.
 
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