Sorry, I've had a visitor and I've been busy elsewhere hence the delay
in this.

An interesting discussion, at least in my book.

Robert Delfs wrote:
>
> An SMB deployed at depth can provide a quite stable platform for
> performing deco and safety stops. (I'm sure deco bars are very nice,
> but I've never dived from a boat that had them.)  Once I've ascended to
> the target stop depth, I find it much easier and more relaxing to go a
> bit negative and just hang from the SMB line without having to
> constantly check computer or depth gauge to make sure I hadn't
> "drifted" up or down.

I'm the opposite, I've never deployed an SMB. Actually I tell a lie, I
did once, well, sort of, maybe ten years ago. Charlie had actually
given me a relatively small lift bag, very open at the bottom which
he adhered, via velcro, to the side of my wing. It was designed to (a)
lift that gorgeous porthole (I'm still watiting for that one to
appear out of the gloom) and (b) act as a DSMB but only in shallow water.

Also, I'm used to deco bars, or shotlines.

Shortly after I got it I decided to "deploy" it, much to the avid
interest of my dive companion (note the expression) on a fairly
shallow, easy, dive in excellent viz. I actually managed to do it
successfully (no reel, just "string") probably through no fault of my own.

The TUG boat knew what was going on. The BWACer's (Brisbane Waters
Aqualung Club), the other equivalent to TUG locally were driving past
and gave this funny yellow thing, bobbing about, very close
inspection. The viz was such, actually, that I could recognise faces
peering down even though I was at 6 metres.

TUG and others (locally) , quite simply, do not dive in those
conditions and, indeed,
currents are relatively rare hereabouts, certainly tropical currents.
Equally, whilst we know that the tide is in, out or whatever, it
really doesn't affect us.

One of the other "religions" rigidly impressed into the mindset of the
TUG divers (and Remora) is:

"Thou Shalt DESCEND The Anchor/Buoy Line And Thou Shalt ASCEND That
Same Anchor/Buoy Line At The End Of Thine Dive".

The caveat being: "If Thou Doest Not, Thou Shalt Swim Back To The Boat
From Wherever Thou Might Find Thyneself."

Remember, we're talking of relatively uneventful temperate water,
carefully checked out. But no, that wouldn't happen in some form of emergency.

> Even a small SMB provides more than adequate lift.  It won't help much
> if the diver can achieve a basic state of neutral (or slightly
> negative) buoyancy on his/her own, of course, but that shouldn't be a
> problem for anyone proficient enough to be doing (planned)
> decompression dives in the first place.  Strong surge or wind
> (particularly if it varies in strength or direction) could be a
> problem, but surge would presumably be an issue with deco bars as well
> - I've certainly seen down lines and anchor lines moving up and down so
> far in rough water that it would have been nuts to try to hang on to
> them at a shallow stop.

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

Sure, here we get to the "Technical" stage. I dunno, what TUG supplies
seems to me not to be technical and in (modern) diving terms they've
been doing it for a helluva long time. Incidentally, on deco dives
there is a hooka to the 12 metre bar from the boat with twin 2nd
stages on it.

A deco dive does not happen, in TUG terms, in such conditions. If it
happens *during* the dive (and it has) those deco bars are a lot
better at giving visual reference (even whilst going up and down) than
precisely nothing to visualise in the water. Most TUG divers that do
deco dives now use some form of Jon line.

I have experienced, on a local deco dive, HUUUGE sudden current and
hung onto the
"bottomest" extremity of the shotline in that extreme situation. That
was quite a long time ago, seems as if we survived.

Not that I'm recommending such a procedure to ANYONE! :-I

Sh*t happened on that day - we had to deal with it.

There have been other occasions of strong current. They, too, have
been dealt with.

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.

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