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I can't let this one slip past.  Carl G. Heinzl writes:

>I often dive deep, especially in the Caribbean, and have been down to
>a tad over 200 feet.  While I did have a glass ceiling for a short
>time on the computer, since most of the dive was considerably
>shallower than this I did not have to perform any required
>decompression stop but did "burn the tank" down to 300 lbs at 15 feet
>(approximately 10 minute stop) just for safety.

You are lucky you did this.  Computers continuously monitor time at depth, and
in this case would take into account the fact the most of your dive was shallow.
If it said you need to hang, then (at least according to the model used by the
computer) you did in fact need to hang.  Unlike tables, computers don't assume
you have spent your entire bottom time at your maximum depth,  which is why the
give you more bottom time than the analagous tables except for square profile
dives.  The down side of this is that they are also less conservative than the
corresponding table, so If you blow off indicated decompression you are
taking a pretty big risk.  Read Aquacorps #1 for a pretty good discussion of
computer use for deco diving.

Note that when people say that computers are more conservative than tables, what
they mean is that the Buhlmann algorithm on which most computers are based
is more conservative than the Navy algorithm on which the Navy tables are based.

John
jheimann@sc*.gt*.co*

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