Need help with Scuba science.

Okay. I can't dive down much below the surface of the pool unless I exhale
because I'm too buoyant. If I exhale I'll go right down, but I can't seem
to exhale and hold my breath so I freak out and need to come right up.
Based on the info I've been reading if I take a few deep breaths I should be
able to exhale and go right down. Seems "science" says that it's too much
CO2 that makes you want to take a breath. Build up your oxygen and you
shouldn't feel the need to breath until your CO2 builds up again.

Now, if I do this I still want to take a breath when I go down. Is this
just a psychological thing because it's more normal for a person to inhale
to hold their breath than exhale? Or, is my science all screwed up?

I guess this would be more of a snorkeling skill, but I want to make sure
I've got the science right. Hope I explained it right.

Thanks

Sheldon

"Sheldon" <sheldon@XXXXXXXXsopris.net> wrote in message
news:Hqmdnb3vk6jnI3XYnZ2dnUVZ_urinZ2d@comcast.com. ..
> Okay. I can't dive down much below the surface of the pool unless I exhale
> because I'm too buoyant. If I exhale I'll go right down, but I can't seem
> to exhale and hold my breath so I freak out and need to come right up.
> Based on the info I've been reading if I take a few deep breaths I should
> be able to exhale and go right down. Seems "science" says that it's too
> much CO2 that makes you want to take a breath. Build up your oxygen and
> you shouldn't feel the need to breath until your CO2 builds up again.
>
> Now, if I do this I still want to take a breath when I go down. Is this
> just a psychological thing because it's more normal for a person to inhale
> to hold their breath than exhale? Or, is my science all screwed up?
>
> I guess this would be more of a snorkeling skill, but I want to make sure
> I've got the science right. Hope I explained it right.
>
> Thanks
>
> Sheldon
>
>

I can't hold my breath or exhale (either one) and dive to the bottom of the
pool,
however, I am a very good diver, with no problems at all becoming and
staying
neutrally bouyant. I don't kick up the bottom, and can easily control my
ascent
or descent. Don't be concerned if you can't just dive down unassisted to
pick up
something on the bottom of the pool.

On Mar 2, 5:08 pm, "Veem" <ginmil...@cox.net> wrote:

> I can't hold my breath or exhale (either one) and dive to the bottom of the
> pool,
> however, I am a very good diver, with no problems at all becoming and
> staying
> neutrally bouyant. I don't kick up the bottom, and can easily control my
> ascent
> or descent. Don't be concerned if you can't just dive down unassisted to
> pick up
> something on the bottom of the pool.

I'm curious. Are you disabled iin some way? I can't imagine not
being able to easily reach the bottom of the pool unless it's as salty
as the Dead Sea and you have no feet.

Sheldon wrote:

> Okay. I can't dive down much below the surface of the pool unless I exhale
> because I'm too buoyant. If I exhale I'll go right down, but I can't seem
> to exhale and hold my breath so I freak out and need to come right up.
> Based on the info I've been reading if I take a few deep breaths I should be
> able to exhale and go right down. Seems "science" says that it's too much
> CO2 that makes you want to take a breath. Build up your oxygen and you
> shouldn't feel the need to breath until your CO2 builds up again.
>
> Now, if I do this I still want to take a breath when I go down. Is this
> just a psychological thing because it's more normal for a person to inhale
> to hold their breath than exhale? Or, is my science all screwed up?
>
> I guess this would be more of a snorkeling skill, but I want to make sure
> I've got the science right. Hope I explained it right.
>
> Thanks
>
> Sheldon

First, a warning: hyperventilating like that before a breath hold dive
is a great way to pass out and drown. Don't do it.

You do a breath hold dive with a lungful of air. This means you're
positively buoyant, which makes it hard to get down where you want to
go. You just gotta work on it. Technique is like this: you swim on the
surface till you see something interesting... a fish or, in the case of
the pool, a used bandaid. First bend at the waist, head down. Ideally
your torso will be vertical. Then kick your legs straight up, pointed
at the sky. Their weight will push you down fast... be ready to
equalize your ears (which ain't easy, in a head-down position).

This will probalby take a lot of practice. But it is fun!

"Paul Foley" <paulfxfoley@earthlink.net> wrote in message
news:9i4Gh.5735$PL.1938@newsread4.news.pas.earthli nk.net...
> Sheldon wrote:
>
>> Okay. I can't dive down much below the surface of the pool unless I
>> exhale because I'm too buoyant. If I exhale I'll go right down, but I
>> can't seem to exhale and hold my breath so I freak out and need to come
>> right up. Based on the info I've been reading if I take a few deep
>> breaths I should be able to exhale and go right down. Seems "science"
>> says that it's too much CO2 that makes you want to take a breath. Build
>> up your oxygen and you shouldn't feel the need to breath until your CO2
>> builds up again.
>>
>> Now, if I do this I still want to take a breath when I go down. Is this
>> just a psychological thing because it's more normal for a person to
>> inhale to hold their breath than exhale? Or, is my science all screwed
>> up?
>>
>> I guess this would be more of a snorkeling skill, but I want to make sure
>> I've got the science right. Hope I explained it right.
>>
>> Thanks
>>
>> Sheldon
>
> First, a warning: hyperventilating like that before a breath hold dive is
> a great way to pass out and drown. Don't do it.
>
> You do a breath hold dive with a lungful of air. This means you're
> positively buoyant, which makes it hard to get down where you want to go.
> You just gotta work on it. Technique is like this: you swim on the
> surface till you see something interesting... a fish or, in the case of
> the pool, a used bandaid. First bend at the waist, head down. Ideally
> your torso will be vertical. Then kick your legs straight up, pointed at
> the sky. Their weight will push you down fast... be ready to equalize
> your ears (which ain't easy, in a head-down position).
>
> This will probalby take a lot of practice. But it is fun!

Uh, unless your BMI is really off, you should go down with a full breath.
Try what Paul said, but if you can't go down then, better talk to your
instructor to see what the problem is.
Best of luck in the class! Dan

On Mar 2, 6:25 pm, "Danlw" <dan...@nospamcomcast.net> wrote:

> Uh, unless your BMI is really off, you should go down with a full breath.

Yeah, that's what I always tell the ladies.

"Greg Mossman" <moss...@qnet.com> wrote:
> "Veem" <ginmil...@cox.net> wrote:
> > No, i mean in my pool. i think my b--bs keep me from being able to dive to
> > the bottom when i am swimming-
>
> That rude obnoxious Grumman will now be around to ask you to post
> pictures. If you'd rather, just e-mail them to me privately.


If they're nice bibs, I'll host them on the rec.scuba photo gallery
page if you send me a copy. They can even be clothed


A bit more seriously,

A human body is pretty close to neutural buoyancy; a person's lung
volume is usually 'just enough' to push us over/under this buoyancy
balance point in freshwater.

Saltwater, being more dense, tends to create a slight positive buoyacy
bais. So too do body compositions with (euphamistically) 'higher fat
content', since fat is less dense than muscle.


What to do about it?


One option is to alter your body's net effective density. Exhaling is
the quickest way, but can have some complications and limitations. If
nothing else, you have a smaller reserve of O2 in your lungs for your
blood to exchange with, so the time you can stay underwater is
reduced.

The second option is to wear some ballast. Essentially the same thing
you do to counteract additional buoyancy from adding a wetsuit.

However, for both of the above, something to keep in mind is that the
air remaining in our lungs will be compressed by ambient pressures as
we go deeper, so as we freedive, our bodies lose some of its natural
buoyancy. As such, even with a full breath of air, we may not
necessarily still be positively buoyant when we are, say, 20fsw or
deeper. As such, adding extra ballast has to be done cautiously.


The third - and IMO best for snorkeling - option is to "use what you
have" better. In general, what I'm referring to here are techniques
such as surface dives.

The basic physics behind a surface dive is that you're lifting part of
your body (your feet) out of the water, where since they are now
sticking out in the air, they're not displacing water, so this will
act as a force to push the rest of your body further down into the
water.

Performed reasonably quickly, and you'll overshoot your neutral point,
which is a good thing because what you do with a surface dive is to
then kick your feet to drive you under. Fortunately, the jacknifing
for a surface dive gets you pointed straight down with your fins
behind you, so you're now pointed in the direction you need to go with
your fins in the orientation to be the most efficient.


For a few body-types, just getting down to the bottom of the pool is
enough of a pressure change to compress the air in their lungs and
they can hang out at the bottom, looking for quarters in the drain.
Most of us will start to float back up as soon as we stop kicking,
although at varying degrees. Sometimes, a short exhalation 'burp' can
be useful then to trade-off some O2 supply because it can reduce
exertion level (the demand for metabolizing the same O2).

Just be careful when experimenting. You don't really need to
hyperventillate for any of this.


-hh

On Sat, 3 Mar 2007 08:58:23 -0700, "Veem" <ginmill01@cox.net> wrote:
> hey, no problem. one advantage, when we had to tread water/float for the
> dive pre-lims, I could go on forever

You make the claim in public, you have to post the pictures in
public... <dirty-old-man-grin>

http://home.myspace.com/index.cfm?fu...59A07882736256


"Grumman-581" <grumman581@DIE-SPAMMER-SCUM-gmail.com> wrote in message
news:ekbju2dfk2i03m8dg9353ni0abobkt4s32@4ax.com...
> On Sat, 3 Mar 2007 08:58:23 -0700, "Veem" <ginmill01@cox.net> wrote:
>> hey, no problem. one advantage, when we had to tread water/float for the
>> dive pre-lims, I could go on forever
>
> You make the claim in public, you have to post the pictures in
> public... <dirty-old-man-grin>

On Mar 3, 12:45 pm, "Veem" <ginmil...@cox.net> wrote:
> http://home.myspace.com/index.cfm?fu...=ZG9tYWluPWNve...


That's only the page for yourself You need to give out your 'public'
URL, which should have a format of:

http://www.myspace.com/{nine digit number}

It should be listed for you on your myspace homepage.



-hh