-> What i would request is comments on ways to keep from losing a
-> location, as this was the outcome.
This is a pretty common problem.  The solution pretty much depends on
when you're looking to find the area the second time.  If it's soon,
it's relatively easy.  There's a commercial product on the market which
consists of a weight, float and line to attach the two.  It's small
enough to fit in a BC pocket.  It's slightly negative, but that's a
penalty you have to pay in order for the weight to hold it in place
against light current, wave action, etc.  For longer term marking, I
recommend a Gallon Clorox bottle and a heavier weight.  Not only is the
bottle easier to see, you don't mind losing it as much if someone
recovers it for you.  You always have the option of attaching a small
strobe to it for night work, but then you're back to wanting to be sure
you can recover it.
For longer term location, you've already done the best thing you can.
While it's difficult to reach a site the first time with a loran, using
someone else's numbers, it's easier to return to the same spot using
your own.  Lorans are pretty good as far as repeatability goes, but they
vary from unit to unit, even by the same manufacturer.  My loran has an
adjustment which helps.  Say I'm trying to find an unmarked site from
someone else's numbers.  If I know the location of an easily found
marked site using the same persons numbers, I can go to that location,
adjust my loran to the other persons numbers and then find the unmarked
site relatively easily.  In short, I adjust my loran to match the one
the original numbers came from.  My GPS is not so convenient.  Selective
availability means that I can't count on being closer than about 100
yards from where it says I am.  When you're looking for a small site,
that can be a lot of variation.  Differential GPS, radio signal
adjusted, can be much more accurate, but I can't comment further since I
don't have any direct experience with one.
Neither the loran nor the GPS is likely to put you right on your site
every time, or even most times.  It will get you close.  That's where
your depth/fish finder comes in.  If I'm serious about finding a site,
I use buoys again, here's how.
I prepare two bleach bottle/weight floats in advance.  When I get to
where my loran or GPS says the site is, I drop the first one.  I then
set up a search pattern around that site, watching the fish finder
carefully.  When I spot the contour which tells me I've found my site, I
drop the second one.  I then recover float number 1, anchor off the
wreck/reef to avoid damageing it and proceed with my dive.
This is all pretty basic stuff, so I may have told you things you
already knew, perhaps misunderstanding your need.  If so, sorry.  If
not, perhaps I've helped.
> Comments on Loran vs GPS would also be invited.
The biggest problem with loran is that one unit does not give the same
readings as the next.  It can, and often does, get you very close to a
spot you've been to before (as in your case), but is much less effective
for finding a spot you've never visited before.  By using someone else's
numbers, I've occasionally been as much as a mile from where I wanted to
be.  Using my own numbers, or adjusting my loran to match someone else's
by checking the difference at a known location I can find, I've been
able to get quite close to what I wanted pretty consistently.
Lee
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