Bouyancy and Holding Breath...

[DA Aquamaster]

I agree your normal breathing pattern should involve fairly fulll lung volume for efficiency purposes. But if for some reason you need to maintain a precise hover, smaller breaths for the short time required and timed to cancel each other out are the way to go. Smilarly, if you are neutral a couple feet off the bottom and want to drop to the bottom to pick up someone's lost dive watch for example, you can do this by exhaling slightly to sink then inhale slightly to stop the descent then inhale more to rise off the bottom again. No finning or deflating/inflating the BC should be required and you should be able to do the whol evolution without touching the bottom or even stirring up any silt.

Over time, if you work at it and dive often, you develop a feel for the rates and changes in bouyany related to the breathing cycle, depth and other factors and will be able to detect if you are rising or sinking too much or too little when you inhale or exhale and will intuitivley know if you need to add or subtract a small amount of air from your BC to maintain "neutral" bouyancy. And by that point you will realize that neutral bouyancy is an average condition in a dynamic system rather than an exact or fixed condition.

It takes practice and a willingness to pay attention to the small details. The fact that you are here asking the questions indicates you are willing.

 

[String]

Ive not really noticed any affect at all on my SAC, at least other factors far mask it (such as current, cold, what kit or extra weight im lugging for someone else etc). Re-reading my description i didnt really write it as i intended and --tom-- rephrased it into what i meant. Ive seen people take totally full and totally empty lungs and that leads to them starting to rise by the time the lungs are full and starting to drop by the time theyre fully empty resulting in a small but noticable yo-yo effect. The rhythm method described is more akin to what i do.

I see what youre saying. I think I could manage this, Ill have to try that. I think Im more reactive as in opps, Im getting closer to that coral...BIG BREATH IN...up and over...now Im too far up...breath out to go closer, little breaths in to stabalize my decent.

The key to solving this issue is anticipation and it does come with practice. After a while you begin to work out just how soon to breathe in to clear an obstacle and when to start breathing out to stop the rise so you arent constantly chasing the desired depth and overshooting on the up and down. The only real method to learning this is diving and lots of it - it will come realtively quickly with practice. You need to be pro-active as opposed to re-active with the breathing. In a way its like flying a big plane, driving a big or heavy car etc - you have to "fly" a few seconds ahead of what is actually happen as your actions take time to have an affect - failing to do so means youre constantly chasing the desired profile.

Its easier done than written here though

 

[jagfish]

Nice post...

 

[Charlie99]

Smilarly, if you are neutral a couple feet off the bottom and want to drop to the bottom to pick up someone's lost dive watch for example, you can do this by exhaling slightly to sink then inhale slightly to stop the descent then inhale more to rise off the bottom again.

No finning or deflating/inflating the BC should be required and you should be able to do the whol evolution without touching the bottom or even stirring up any silt.

This sort of exercise will also give you a better feel for the delay as a breathing-induced buoyancy change starts to take effect. It takes a while before an inhalation will reverse your descent, and if you wait until you are right at the bottom, you will bounce off of it rather than gracefully stopping just short. Controlling depth by breathing takes a lot of anticipation, but it's that same delay or averaging effect that allows you to stay close to one depth while hovering.

 

[RTW]

Control buoyancy, watch your air, time, and depth, keep track of your buddy, see the sights............Who said you don't have to multi-task while diving?!? :439: