That's an unknown-to-us, because Suunto doesn't document/publish their
full algorithm in open literature.  However, what I have observed is
that I can have a couple of days of 2-tank AM dives and then the next
day, instead of it being #1, #2 again, it starts with #3, #4, #5,
#6, ... until I take a full break day off.

Given this change in behavior of the machine, along with perceived
shorter no-stop times, my conclusion is that my bottom times are being
penalized within some aspect of their algorithm.

Could be that too, although this was a member of staff, and had been
doing the job for years...the resort was short on personnel, so they
weren't getting their usual break day(s), hence the very long
continuous cycle of daily diving.

My point is merely that the human biological machine is a very complex
one that we still don't even fully know how all of its chemical
processes work on the surface, even before we muck them up with
hyperbaric exposure.  It could very easily be some enzyme that we
don't even know exists yet, for the simple reason that we've not known
to look for it.

That's a young man's sport .. although in a similar vein, I can now
give you detailed directions to an establishment in Brussels that has
500 different kinds of Tequila available.  Not that we tried it, but
their most expensive was EU 90 per shot.

-hh

Just semantics possibly.  Even if the time to fully desaturate is
computed as less than 24 hrs, the computer will still sequentially
number the next day's dive in the same series because a different
algorithm tells it that the dives are part of the same dive trip.
I.e., just because the next dives are numbered 5 and 6 doesn't mean
the decompression algorithm hasn't necessarily reset itself.  Yes, the
deco part of the computer is probably still tracking the dives after
24 hrs, but how much is it really penalizing the diver for
"repetitive" diving with such a long interval in between?

Or your anecdotal "friend" was an off-the-charts exception to the rule
that we all know happens occasionally.  Sure, most vacations aren't
that long, but I can't believe there haven't been enough Navy studies,
DAN studies, etc. that longer-term effects couldn't be extrapolated
effectively into a computer model.

But there have been enough hyperbaric studies on humans and other
mammals that we would know if there are any major such bodily
processes that are affected by diving.  No need for hypotheticals when
we have willing Navy "volunteers" :)

Now real world experiments would have us get the Navy sailors drunk
every night, maybe make them smoke cigarettes between each dive and
eat lots of fatty fried foods, and refrain from any sort of exercise
in between dives that might make them more approximate to certain dive
vacationers.  When the Navy starts doing those sort of experiments,
I'll volunteer!

I'd be inclined to say that my Suunto seems to think so:   even the
typical 2-tank AM diveboat schedule has gotten it to the point where
its saying that Day "N" is Dives #5 and #6, since it didn't reset back
to #1 and #2, since with the same start time each morning, there
wasn't a full 24 hours between the first dive of the day and the end
of the second dive on the prior day.

In general, I don't really believe that there should be all that much
risk from 2 dives/day ad infinitum, but particularly since I had a
friend get a career-ending DCS-II hit on just such a regimen (IIRC,
around 20-30 days in), so I do have to believe that it would seem to
contain some unknown factor that somehow comes into play on such long
regimens.  This is despite how it should seem that spending 90% of the
time (20+ hours) out of the water each day should logically make this
a moot issue.

In short, I think this is a "we don't know enough" issue, in part
because the profiles ... weeks of repetition ... are generally
uncommon, which gives us less insight of the risk to work with.  My
personal hunch is that its not really a "really long compartment" in
the classical sense, but that all dives do some sort of discrete
'damage', and while this isn't a factor for "short term" dive series,
it can become one on a loooooong series.

For example, hypothetically consider a situation where our body
couldn't make red blood cells in our bone marrow while we're under X
pressure/depth.  To lose a few hours worth of production once in
awhile ...or even a few days in a row...isn't generally a problem for
us, but if we were to dive every day...even for only 2 dives (2
hours)...the accumulation of this shortage over several weeks could
potentially cause a body to become anemic.

-hh

Maybe, but that begs the question of whether or not this is a
desirable practice, i.e. does it make a difference in safety to take a
day break over 3.5 weeks of making two dives a day.  My feeling is
that it probably is a good thing to break up an intensive dive
schedule of four or five dives a day like you might do on a typical
liveaboard or at a dive-intensive resort or locale like Cocoview
(Roatan) or Bonaire, but doing two recreational-depth dives a day in
the morning followed by 20 or so hours of offgassing before the next
dive day can probably be continued far longer than 3.5 weeks without
imposing any undue health risks.  Thoughts?

And don't forget that William Tell fellow who would shoot apples off
people's heads for fun.

It does sound a bit odd, but perhaps we are reading a bit too much
into language translation - for a Swiss, French, German & Italian are
their official languages, so English is probably in 3rd or 4th, with
the country's 4th language of Romanish being less common overall.

Being that it was a midweek break, I recall that there are "take a day
off" recommendations from DAN, etc, so I think that this could be that
they were simply electing to take a mid-trip break day, but what got
lost in translation was the explanation of "who" (man vs. computer)
was calling for it.

The Swiss may come off as conservative & reserved in some things, but
there's some real surprises when you really start to look.   For
example, if they were so paranoid about personal safety, they wouldn't
have had explosives in place wired to blow tunnel in the country up
through the 1990s (& later).  Similarly, lets not forget that it was
the Swiss who did some of the earliest diver-test trials with trying
to figure out DCS ... and I believed that I mentioned here awhile back
that I had the pleasure of meeting one of those original military
divers a few years ago...one of the ones who got pretzeled, IIRC, due
to a post-dive increase in altitude.

-hh

On Feb 1, 4:14 pm, Alan Browne <alan.bro...@FreelunchVideotron.ca>
wrote:

See, that's just plain weird.  However, Swiss are known to be
extremely conservative.  Since most computers can be programmed for
extra-conservatism, even Suuntos, it's possible she had hers
programmed to ensure she had extremely low residual nitrogen.
Nitrophobic!

====================
The reason for her conservatism is obvious.
She's Swiss.
There are airliners that don't fly as high as her house.
hoges in WA

On Feb 1, 4:14 pm, Alan Browne <alan.bro...@FreelunchVideotron.ca>
wrote:

See, that's just plain weird.  However, Swiss are known to be
extremely conservative.  Since most computers can be programmed for
extra-conservatism, even Suuntos, it's possible she had hers
programmed to ensure she had extremely low residual nitrogen.
Nitrophobic!

No, it was mid stride.  They programmed a 2 day out before flying to dry
out their wetsuits...

I've put my Suunto Vyper into Deco .. I've never had it insist on any
sort of huge surface intervals, which does make this sound like the
Swiss Lady likely had some sort of violation, so the computer locked
her topside.

Of course, a magnitude of 31 hours also kind of sounds like it could
have alternatively been a "Time to Fly" time requirement; if this was
the cause of her skipping her last day of holiday, this could be
another possibility.

Given how conservative the Suunto is even at its most liberal
settings, I'd generally be more concerned about losing a day of diving
for it locking up, than the DCS risk from not fully completing its
deco schedule.

BTW, if you do put a Suunto into Deco, do be aware that it is
surprisingly fussy about your hang depth:  you really need to get up
to the top of the glass ceiling in order to clear the stop in anything
even remotely close to the time that it says it will take.   IIRC, my
first experience was something like an 8-10 minute obligation, which I
did at my usual 15-17fsw safety stop depth, but which after ~15
minutes, hadn't budged more than a few minutes...so I came up to
~11fsw and it took around another 10 minutes to clear the remaining 7
minutes or so.   All told, I had nearly a half hour hang at <20fsw
before it was finally satisfied, and that was from a profile that
probably was within the ancient USN Table's no-stop limit of "25 min @
100fsw" square profile...so how much DCS risk was there, really?

They were what...all of 3ft long?  :-)

-hh

On Jan 29, 3:03 pm, Ecnerwal
<MyNameForw...@ReplaceWithMyVices.Com.invalid> wrote:

If you've never run a Suunto into deco, you must dive conservative!
But deco or not, I never argue with my Suunto.  Perhaps that's what
Alan's Swiss lady friend did; maybe her 31-hour imposed surface
interval was because she screwed up.  I hadn't considered that.  I
even try to obey the optional deep-stop recommendations on my D9, and
would rather profane God than disobey a mandatory imposed deco stop.
Normally it's NDL all the way to the surface, but I've had it
occasionally impose a 1-minute mandatory "safety" stop on dives when
I'm ascending directly rather than taking my time exploring shallower
realms on the way up.  I usually dive nitrox, so it's only made it
into unplanned deco a few times, but when I dove the Spiegel Grove
using optimal nitrox mixes (29% for a bounce to 140 on the first dive,
followed by 35% for a max of around 90'), the bastard stuck me with a
minute at 20' and 8 minutes at 10', right when there were 6 man-eating
huge barracudi at 15' on the mooring line.  I turned my back to the
sinister fishies and did my time.

There are conservative computers, and there are aggressive computers.
Buy one to suit your personal style. One reason to use a conservative
model is that people do get bent diving within the bounds of tables and
computers - this should have been mentioned in class.

But if you are an aggressive diver and buy a conservative computer, you
will probably just ignore it and go diving when it's locked you out for
a deco violation - I've certainly see people do that. As such, an
aggressive diver should choose an aggressive computer, so it's at least
of some use to them. But an aggressive diver is inherently more likely
to get bent, period.

The recreational tables are not really formulated with an eye to diving
every day for nearly a month. Many people choose to take a day off (or
limit it to a half-day of diving) in the middle of a mere week of diving.

Computers can also penalize you for the things you *actually* do, as
opposed to the nice clean plan you didn't actually follow - for
instance, if you ascend faster than you should on tables, the table
doesn't know that. If you ascend faster than you should with a computer,
it can slap a fudge factor on your surface interval to allow for that.
My conservative (Suunto) computer will penalize for ascent rate, lack of
safety stop, insufficient surface interval and several other things as
well as actual missed decompression stops. The latter would be per the
manual, as I've never run it into decompression - it and I are well
matched.

Screwing up threading to save a post:

That's "independent tests by other people" - the aforementioned Rodale's
for one. The methodology seemed pretty decent. They were specifically
trying to get past the vague claims of of manufacturers.

They've done it for several years: here's 2005
http://www.scubadiving.com/gear/2007/03/2005-fin-test
http://www.scubadiving.com/gear/2006/11/2005-fin-test-protocols

I don't actually own a pair, though my wife does. I have used hers when
I was surface snorkeling and she was sitting on the boat, and my
impression is that they are better than the paddle fins I use. Since I
can outswim her with the ones I use, and we almost invariably are each
other's buddies, there's no point in me getting any, at least until
these ones break.

First, thanks for all your replies, gents.  Very educational.

The Swiss couple I met (and usually had a drink or three with almost
daily) insisted on the merits of their computers.  The lady, one day,
took a full day out of diving (they were there for diving only over a
3.5 week period) as her computer told her to take a 31 hour surface
interval.

She had been making daily deep dives (first dive) to 100 - 130 feet
almost daily followed invariably by a shallower dive 30 - 60.

As I learned to use the tables and 'chain' successive dives together, I
could see no trend indicating that one would accumulate a large required
surface interval.  At least not on the basis of two dives per day, the
first being to 130'.

So the question goes, are the computers too conservative?  (Tables too
loose?).  I know the computers also "give" as they integrate finely and
give "credit" for the fact that a 45 minute dive to 130 feet is not all
spent that deep, but it seems in integrating overall tissue N2 they are
too conservative.

The second question goes, the Swiss told me there are places in the
world that will not take you out diving unless you have a computer.  Is
this so?

Thx.