Question regarding neutral buoyancy

[chimong]

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?

 

[Manatee Diver]

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.

That is a bad idea. Once you've roughly attained neutral with your BCD, the fine control should be done with your lungs. A little too buoyant breath out more air than you take in with each breath. Too negative, do the opposite, breath out less than you take it. Sure you will have times when you mess it up, but we all do when we first start.

 

[wetb4igetinthewater]

The amount of weight is the amount to keep you at your safety stop with an empty BCD and a nearly empty cylinder (50 bar). The weight should be distributed so you float effortlessly horizontally.

 

[napDiver]

I was dealing with newer divers earlier and the issue is really an event that causes your breathing to bring you up.

1) get neutral and hover above the floor for 5 seconds.
2) be aware of depth changes. If you go from 100 to 90 ft, not much change in your bouyancy but if your in the shallows and go 30 to 20 ft or 20 to 10 ft ur bouyancy will change a lot.
3) do not dump air from your bcd once you hit the bottom, unless your ascending. Try your best not to. But if #2, and it seems like your about to float up uncontrollably dump some air.

After about 10 dives you should get much better at this. The issue is your breathing and then the second is the issue is exacerbated by the air in your bcd and wetsuit. Hope that helps

 

[lexvil]

Just keep diving, make adjustments and pay attention to how each thing effects you, experience is the best way to get it right.

 

[napDiver]

I read your post again. If you are going to be doing a shallow dive and have uncontrollable ascent issues, you can add a couple pounds as training wheels for 5-10 dives.

After that I would insist you always keep yourself properly weighted. If you are diving deep, do not add even 1 lb.

 

[wetb4igetinthewater]

This is a basic scuba page, so I won't express my honest feelings to adding "a couple lbs" other than say don't.

 

[PfcAJ]

It takes practice.

you’re correct that if you’re neutral, on the inhale you’ll be positive and negative on the exhale.

but overall, you’re neutral. And that’s what matters. You’ll sort out over time how to control you buoyancy with your breath cycles

 

[James79]

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.

I'm not an instructor, or an expert, by any means... but I will touch on the physics of this. When you float up a bit much it got harder to get back down.... due to the air in you BC expanding. If you were negative and descend, the air in the BC compresses and you get more negative. If you add extra weight, you will end up adding more air in the BC to offset it.... and that greater amount of air expanding and compressing with depth changes will result in a greater buoyancy swing. Which is why proper weighting makes buoyancy way easier.... It minimizes the air in the BC, and therefore the buoyancy swing from depth changes.

Respectfully,

James

 

[FishWatcher747]

The most helpful thing I can say is I had the same problem in my first few dives. I just kept diving and it went away. I became more aware of my buoyancy and the moment I started to ascend I would exhale longer .

Once you get significant momentum of ascending just an exhale may not counter the momentum. Then dump air from BCD to compensate.

One thing to learn is to use the dump valve on your hip (probably right hip in jacket BCD). When you start ascending out of control face down towards the bottom, fin downward and if you need to use the dump valve on Right hip to gain neutrality again.

Good luck, this is normal progression.