What Happens when you Take your BCD off at Depth

[Steve_C]

Other than doing it a couple of times to make sure I know how to do it I do not routinely do it. I have integrated weights so easy to remove and replace pockets. If I have dive shorts on I let air out of BCD and put the weights in the shorts. If I do not have shorts on I put the weights inside my wet suit. Not ideal but it works. Point is to keep the overall weight the same and stop anything from being too buoyant. Depending on the wet suit I have on (anywhere from 3 to 7) I have the option of putting whatever amount I want in the wet suit or on the BCD. About the only reason I can see wanting to do it would be a really bad line entanglement but that is a good use for a buddy. The few times I have had to deal with it by myself by going slow and careful I handled it with no donning or doffing needed. (Buddy was available but good practice to do it myself if possible)

 

[MichaelMc]

1. Why are we ascending? If so, why are we not exhaling?

2. I give up.

 

[IncreaseMyT]

1. Why are we ascending? If so, why are we not exhaling?

2. I give up.

Is there anyone else here that is negatively buoyant at depth with a breath of compressed air and no weight and no BCD?

I am sorry I don't know how it is possible, in fact all these posters are suggesting putting weight on your persons because of this, yet you are saying it is not true.

Some people can free dive without weights, if they don't have a wet suit. BUT they are still positively buoyant when they ascend, they just kick past their neutrally buoyant depth. Most free divers don't do this though because it is costing you energy and shortening your breathe hold.

So your friend must be the only person in history that is negatively buoyant at depth with a breath of compressed air, so I too give up.

 

[Scuba Lawyer]

Back in the days of horse collar BC's (or no BC at all) we would routinely take our tank off, leave it outside a lobster cave, and slither in breathing off our 20-foot primary hose. Today (and excluding weight integrated BCD's), if one is weighted properly, there shouldn't be any air (or just a few squirts) in your BC at depth. As long as you void your BC of air there shouldn't be any issue with a change in bouyancy. If you have a weight integrated BC and take it off at 30 feet with a 7 mm suit, grab on, hang on, and get your E-ticket out (I exaggerate to a degree but the image of Wyle E. Coyote trying to get the Roadrunner with anvil and balloon comes to mind).

 

[Charles2]

It's actually a huge difference, because his lungs are full at depth with compressed air. He will no doubt be positive, and become more positive as he ascends.

You sound like my eighth grade science teacher when we did the chapter on buoyancy. When he said "If you put enough air in a scuba tank, it will eventually float". He went on to teach English literature in a nearby college.

By the way, I am negatively buoyant at depth, although I don't breath compressed air, I only breath air at ambient pressure.

 

[sea_ledford]

Is there anyone else here that is negatively buoyant at depth with a breath of compressed air and no weight and no BCD?

I am sorry I don't know how it is possible, in fact all these posters are suggesting putting weight on your persons because of this, yet you are saying it is not true.

Some people can free dive without weights, if they don't have a wet suit. BUT they are still positively buoyant when they ascend, they just kick past their neutrally buoyant depth. Most free divers don't do this though because it is costing you energy and shortening your breathe hold.

So your friend must be the only person in history that is negatively buoyant at depth with a breath of compressed air, so I too give up.

Yes, there are a lot of people that are negatively buoyant without weight. It is simply a matter of body composition. I used to use 2 lbs in salt water with a full 3mm suit on, and I have never been even mid- teens in terms of body fat percentage. I just have a negative attitude. Guys that are super lean will sink like rocks. Muscle sinks, fat floats.

One of my current students wore a 3mm full suit with a 3mm shorty over it for openwater dives. No weight, still negatively buoyant. Everyone loved working with him in rescue class.

-Chris

 

[IncreaseMyT]

Yes, there are a lot of people that are negatively buoyant without weight. It is simply a matter of body composition. I used to use 2 lbs in salt water with a full 3mm suit on, and I have never been even mid- teens in terms of body fat percentage. I just have a negative attitude. Guys that are super lean will sink like rocks. Muscle sinks, fat floats.

One of my current students wore a 3mm full suit with a 3mm shorty over it for openwater dives. No weight, still negatively buoyant. Everyone loved working with him in rescue class.

-Chris

Yea because he had a BCD on. and he wasn't breathing compressed air at depth. One of my friends I dive with is about 6% body fat, he goes inverted the minute he takes off his BCD. It actually works out cause then you can work on your rig easily.

We are talking no weight, no BCD and take a breath at depth. You're going up, nothing you can do about it.

 

[Dan]

There is not a person that dives that will not be positively buoyant with a breath of compressed air at depth, with no weight. Most really good free divers are super lean, and they need weights too.

Without some type of weight, you will ascend, and as you do you will become more positively buoyant, unless you did not go down on a scuba tank and your lungs have collapsed, and you have then became negatively buoyant because of that. No wetsuit and yes you would be less positively buoyant, but you would still be positive.

Not true! Once you pass certain depth, like 100’, freediver like William Trubridge will be negatively bouyant. Check this video clip out

 

[IncreaseMyT]

Not true! Once you pass certain depth, like 100’, freediver like William Trubridge will be negatively bouyant. Check this video clip out

I already explained all this Dan. The reason he becomes negatively buoyant is because his lungs collapse to the size of a plum. When breathing on your regulator at depth, that doesn't happen. Right?

 

[caruso]

We are talking no weight, no BCD and take a breath at depth. You're going up, nothing you can do about it.

This is completely and utterly wrong. As decribed by others. Once many or most divers get past a certain depth theyy will be negatively buoyant with a lungful of air while wearing no weight.