Question regarding neutral buoyancy

[Celt]

How is commercial diving relevant to a discussion on recreational diving?

Diving is diving and buoyancy and trim are just tools to get the job done, there’s no right or wrong buoyancy and no right or wrong trim.

 

[wetb4igetinthewater]

Diving is diving and buoyancy and trim are just tools to get the job done, there’s no right or wrong buoyancy and no right or wrong trim.

Key word is job. Commercial divers often have to work on the bottom. Wear those leaded shoes. Sure my Hollis F1s are fairly negative, but not that bad! I wouldn't want to see that commercial diver on a reef.

 

[Blackcrusader]

Diving is diving and buoyancy and trim are just tools to get the job done, there’s no right or wrong buoyancy and no right or wrong trim.

Didn't we have these discussions? I think mastering ones buoyancy is pretty important. Trim is another discussion we all know my views on that I dive with lots of vacation divers who are not the best divers but they are happy divers and yes take their fish photos.
Some are on their bucket list vacation where doing a few days of diving is on the list.

THE "PERFECT ( being horizontal ) TRIM" HOAX

Buoyancy question how do you maintain a sitting hover?

 

[Carlos Danger]

Hello. Relatively new diver here who recently finished padi aow. I used most of my aow dives to improve my buoyancy skills and I have one question:

After establishing neutral buoyancy, your body still ascends or descends as you inhale or exhale. Maybe I inhaled too much or at the wrong moment, I started to ascend more than I would like and it became difficult to bring myself down again. This happened a few times during my dives and I had to pull the exhaust valve quickly to prevent myself from continuing to ascent.

Afterwards I asked my instructor that to avoid this problem, if it's better to remain slightly negative buoyant. With slightly negative buoyancy, you can be neutral when you inhale. When you exhale, you will descend but you can easily control it by kicking. And you don't need to worry about accidental ascending anymore. My instructor said it's ok.

I want to ask if this is a right approach to neutral buoyancy. If not, what's the problem here and what's the correct thing to do?

To help OP with his/her initial concern: what you describe is true BUT the key is hidden in what is called inertia (I think that is the correct term - sorry English is not my first language).
Yes assuming you are perfectly neutral, once you inhale you will start assenting (and descending as you exhale from neutral), BUT there is a lag (i.e. it takes some time) between the two due to inertia. Also, your body with all the equipment etc has a big surface and hence it needs quite a bit of force to move through water. Hence from the moment you inhale (which also is not instantaneous by itself) it takes some time for the upwards momentum to build and then you start moving up noticeably. The art of breathing uw is that with some practice you will learn to "predict" the building of this momentum and counteract it (eg start exhaling at the right moment) before you even move upwards noticeably. Not only this, but you will eventually learn to use this to your favor eg to initiate and maintain slow and controllable ascents or descents with minimal effort.

The problems with new divers (occasionally myself included) is that they get neutral (or think they do) then fill in their lungs with a deep breath, then pause and think to themselves: "what is going on now?" after few moments upwards momentum builds and they think, "oh, I am moving upwards" and then "oh sh*t, maybe I am underweight", after few more moments: "I am now going upwards even faster now, I am definitely underweight" and so it goes. By that time a slow (for the time being) uncontrolled ascent has started - if they realize it on time they can still stop it, but quite often (eg if they are destructed by a nice fish, or while taking a selfie with their go-pro or dealing with an equipment issue) by the time they do it is already too late.

To solve this the diver shouldn't have started with a deep breath to begin with - just a normal breath should do. Then once the inhale is finished and once (or actually even before) you feel the upwards momentum building you should have already initiated your (slow) exhale (to counteract the building up of upwards momentum). With a bit of practice you will see that (normal) breathing won't affect much your buoyancy.

I know that all these are easier said than done, but at least that is what is going on.

I hope it helps.

Stepfen's comments are pretty close to where I was going to go with this topic as well, but in some ways I look at the title of the post and what the op is actually asking about as two different things. It strikes me that where neutral buoyancy is largely about achieving static balance, breathing technique relative to buoyancy is more about dynamic control.

Our sense-of-timing is a factor that does not get mentioned very often in the context of buoyancy. Developing a feel for the delay in movement that occurs as a result of breathing, and somewhat counterintuitively anticipating its' reverse effect on your positioning and trim in the future, is one aspect we are not always sensitive to as new divers. However, I think learning to effectively control buoyancy relative to each person's individual dynamics can be a bit of a moving target when it comes to getting advice. If someone is having problems with buoyancy control, developing good breathing technique is probably not entirely going to be the fix. There are a number of other factors that go into the equation, and these can vary from diver to diver. Your overall equipment profile is another integral factor. Dialing out inherent buoyancy lowers the need for extra ballast, and this can make a profound difference. Once your equipment starts working with you, suddenly it can become much easier to feel what's going on and responsively anticipate how your breathing in any given moment can affect your buoyancy shortly thereafter.

In my case, I think the moral of the buoyancy (control) story was in looking at some of the reasons why a lot of very experienced divers tend to gravitate towards certain simple tried-n-true equipment choices/configurations relative to the conditions. Once I got the equipment thing dialed, controlling the buoyancy part almost became second nature.

 

[Celt]

Key word is job. Commercial divers often have to work on the bottom. Wear those leaded shoes. Sure my Hollis F1s are fairly negative, but not that bad! I wouldn't want to see that commercial diver on a reef.

Obviously when you teach your students you need a system in place to get the best you can out of them but don’t they need to take what they learned and use it to suit the diving they wish to do. If it’s searching a river bed for lost items ( the ideal buoyancy is heavy) or getting the perfect photo on a drop off ( the ideal trim is vertical)

 

[ginti]

Didn't we have these discussions?

C'm on The OP has a specific question, he is not here to discuss whether buoyancy/trim/ecc. are important or not - sure, we degenerated a bit, but we are SB, aren't we?

By the way, @chimong , did you have the time to dive this weekend? any news?

 

[chimong]

C'm on The OP has a specific question, he is not here to discuss whether buoyancy/trim/ecc. are important or not - sure, we degenerated a bit, but we are SB, aren't we?

By the way, @chimong , did you have the time to dive this weekend? any news?

Hi ginti, I don't live near water so unfortunately I can't scuba dive every week. In fact, I probably won't be able to try out a lot of the stuff suggested here until my next trip to the beach. I appreciate very much the many detailed instructions you guys have posted on this thread regarding how to adjust weight/breathing/etc and just things that won't otherwise be brought to my attention in general.

 

[wetb4igetinthewater]

Obviously when you teach your students you need a system in place to get the best you can out of them but don’t they need to take what they learned and use it to suit the diving they wish to do. If it’s searching a river bed for lost items ( the ideal buoyancy is heavy) or getting the perfect photo on a drop off ( the ideal trim is vertical)

I submitted Sunday a 3-part blog series to SDI about how I teach.NB/T. In it I do make the point that I’m not advocating divers to be horizontal all the time, just when moving. I go in all sorts of positions when I take pictures. The point is to teach new divers to be capable of being trim and minimally weighted for any configuration they need.

I have installed a helix type anchor underwater and yeah it was tough “properly weighted.” Adding weight helped a little but not much. But how many divers will do that sort of thing? I focus on the common case. Now in a search and recovery course, you make a point, but I don’t think that’s appropriate for open water.

 

[60plus]

I don't find it difficult at all to initiate descent at the beginning of the dive. After all, I'm carrying 5 pounds (of air) that I won't have at the end of the dive.

I think the following post (TM Heimer) answered your comment pretty well. I know in theory you have to allow for the weight of air / gas that will be used during the dive but In practice I find there are small amounts of air trapped in bcd, wetsuit or drysuit, dsmb, threads on dsmb reel, inside boots or socks, that gradually come out during the dive decreasing buoyancy. 5 pounds of air sounds a lot but its only the equivalent of just over 2 litres of air in the lungs.

 

[inquis]

As I said earlier, flooding your wetsuit is a good idea before descending. I took TMHeimer's post as agreeing with that. Effectively emptying your BC is certainly a skill one should develop.

With another 5 lb in the tank at the beginning of the dive plus the 2-3 lb from exhaling... I'll simply state that if I cannot get down without difficulty with all of that going for me, then I do not have enough weight to avoid what I consider to be an excessive final ascent rate at reserve pressure (regardless of wetsuit, BTW). As always, YMMV.