Bill Mee wrote:

> That is one of the primary reasons we dive double 80s in the ocean
> because they are as you say  "like corks" when they are empty.  In the
> first place neither I nor George have ever breathed them down to the
> point where emptiness is even a remote issue. In the event we had to
> breath them down to that point it would be because the dive boat had
> left us adrift and those two floating cylinders would give some
> additional comfort while waiting for the Coast Guard helicopter. You can
> easily swim aluminum 80s to the surface without a buoyancy compensator
> if you are using Scubapro jetfins. This eliminates the need for the
> additional bc or other buoyancy device required when you are diving with
> cement blocks on your back. Nobody likes to walk back to shore along the
> bottom.  Furthermore, in the last several years I have never breathed my
> gas below 2000 psi while diving dual 80s in the ocean.

> What we have here is the usual conundrum of one problem begetting a
> recursive series of complications. This is so typical of the situation
> in socalled technical diving. If you dive with very negatively buoyant
> tanks you now need to layer on all sorts of additional safety measures.
> This is akin to driving with a gas can on the front seat of your car
> because the capacity of your main fuel supply in inadequate.  Now to be
> safe you must carry a fire extinguisher and wear an asbestos suit. 
Most steel tanks are only negative when they have gas in them. Most are about
nuetral (+/- 1-2 #) when low or 
empty (operationally). I can swim mine up without my BCD assistance. In your
example with Al cylanders, if you 
do encounter a problem and use most of your contents, then you can't maintain
depth during deco and there is 
nothing you can do about it. And your deco obligation may naturaully be more,
if your situation is an extended 
bottom time and unexpected use of gas available, like if you got lost or stuck.

This sounds to me like the conundrum you allude to above.

If my wieght belt has enough lead on it or I have additional non essential
equipment, e.g. video light 
batteries, with me that are negative enough to counter my suit bouyancy at the
end of my dive when my tanks 
are operationally empty, I will only be negative at the beginning of the dive,
when the tanks are full. That 
is the best time to prevent a problem and also deal with one, such as losing
positive bouyancy capability. And 
the easiest solution to that is a redundant bladder in the BCD. The next is to
ditch some of the negative non 
essential equipment. In any event, the wieght of the gas in anyone's tanks
should not be the wieght that keps 
them form assending. Its usually less than 20 lbs, and everyone should be
cardiovascularly fit to overcome 
that with leg and fin power.

> We DO NOT perform long extreme exposure dives in the ocean. PERIOD.
> I will not, and I know that
> George will not, perform a decompression dive offshore that requires
> anything more than two 40cf bottles of deco gas.

Good for you. Some others want to go deeper places, in the ocean, and there is
nothing wrong with that. If you 
only want to day hike so you will not venture too far from the road without a
heavy pack, etc., OK. Others 
want to and will.

Tom
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