On Mon, 21 Oct 2002 20:12:30 +1100, Christian Gerzner wrote:

[snip]

>Your comment doesn't address the possibility, quite real, of gas
>loss/depletion.

I'm not sure what you mean by this.  Gas loss/depletion from the SMB?
Can be a problem with an open-necked lift-bag, but a lot of
sausage-type SMBs (including mine) have one-way valves.  For the
others, and lift-bags, you just need to keep enough tension on the line
to ensure the SMB doesn't evert and spill air.

...[snip]

>In the UK, as an example, the dive boats virtually never pick in. They
>stand by having dropped their shotlines onto the dive site for divers
>to descend on. Those divers then employ a DSMB to ascend on (your SMB,
>Robert, with "Delayed" tagged onto the front - I say this *not* to
>educate you but some might not know) and the dive boat follows these.
>This is routine in that part of the world where currents and tides are
>much more significant than locally.

Keerect.  I think the DSMB usage is mainly British - to distinguish an
SMB deployed at the end of a dive with what appears to be a common BSAC
practice - towing a surface buoy (referred to as an SMB) around
throughout the entire dive.

I'm talking about tropical diving, Indo-Pacific (my only experience),
where DECO bars aren't common.  At least I've never seen them used,
though I've been on a couple of boats that drop a weighted tank and
regulator over the side in case someone miscalculates their gas
consumption (though I've never seen it used).

>Incidentally we also use "shotlines" locally. But here we (usually)
>pick in and *our* shotlines are attached to the boat, for divers to
>hang onto on deco (of whatever persuasion) and it is not planned that
>they should reach the bottom. If that were to happen, the weight attached
>to them would be negated by resting on the substrate. I guess you
>could call these a "reverse SMB". :-)
>
>Cheers,
>
>Christian


Robert Delfs
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