On Sat, 17 Mar 2001 21:29:30 +1100, Christian Gerzner
<[log in to unmask]> wrote:

>Reef Fish wrote:
>
>> Generally speaking, especially if the vis is poor.
>
>I note the quallification, its a good one.
>
>> For liveaboard diving, we are always brief on where the boat is
>> anchored, but we seldom go to the anchor first because the boat
>> may be arcing back and forth right over the wall, and the anchor
>> may be 100 meters away.  So, it would be really silly to go
>> 100 meters to the anchor and swim back 100 meters to where you
>> entered in the first place.  :-)
>
>Not (mostly) in my experience, here in Oz and those parts of the
>Pacific I've been to. So far I have always been on liveaboards where
>the boat anchors (on top of the reef) and _then_ we dive.

I didn't mean to imply otherwise.  The ANCHOR may be 100 meters
away from the dropoff on a wall, but the BOAT is generally on
the ledge of the wall.

>Since
>(obviously, otherwise the boat would get a sore bum) it is standing
>off the reef I always prefer to descend the anchor line to the drop
>off. Means I get a good eyeful of where the anchor is actually located
>so I will know its not there if its pinged and know the area anyway
>when I (hopefully) get back to it.
>
>> For my type of anchored boat dives, in high vis, natural
>> navigation is far better than compass navigation or using the
>> anchor as the reference point.   Let's say I jump off at some
>> point near the wall, THAT's my reference point.  When I return
>> there, the boat may be 100 meters away from THAT point because
>> it arcs back and forth, but if I just WAIT there, then the
>> boat will eventually return to that same point.
>
>Absolutely, couldn't agree more. I only question the 100 metres bit,
>seems a fairly long anchor line. In my experience anyway.

When the liveaboard boat is 110 feet, it is NOT unusual for the
anchor line to be THREE TIMES the length of the vessel, which
comes to 100 meters.   For MOST of the Aggressor and PhD liveaboard
locations, they are tied to FIXED moorings, so that the down line
to the anchor (or the fixed point) is generally shorter than the
3:1 ratio.


>> >Like the article says, you pay good money
>> >to have an operator put you on top of the dive site, why mess it
>> >up by swimming a long way off from the boat, spending valuable
>> >dive time and air doing the long haul back.
>> >Makes pretty good sense.
>>
>> Makes good sense NOT to swim to the anchor if the boat drops
>> you right on top of a wall, and the anchor is 100 meters OFF
>> the wall.
>
>Well, yes, but are you here saying that the boat has anchored _off_
>the drop off?

Yes!  If the current is flowing AWAY from the wall (the dropoff),
then anchoring ON the dropoff would only mean the boat will be
50-100 meters AWAY from the dropoff, in blue water.

That HAPPENS at times, on FIXED moorings, when the tide is flowing
in the "unusual" direction.   In those cases, divers are advised
to go down the line to the wall, OR wait till the boat arcs to
near the wall before jumping off.

I was on the Crown Diver liveaboard in the Bahamas (a HUGE boat
that went out of business shortly), the Norwegian captain set
anchor over 100 meters AWAY from the wall so that if the current
flows the direction he THOUGHT, the boat would have been right
over the dropoff.  Unfortunately, the (mile) current was flowing
the OPPOSITE direction, so the boat was OVER 200 meters AWAY from
the wall.   On that particular dive, most of the divers, including
the Norwegian DMs (who knew nothing about the Bahamas sites :-))
never found the wall!  :0(   That's only ONE of the reasons that
the Crown Diver and Crown Islander (sister vessels converted to
dive boats, with cabins at least twice the size of regular hotel
rooms) didn't stay in business long.

>
>In the Oz Coral Sea for example that could well be 1000 metres of drop
>off, an impossible depth to anchor in, for any boat.

You obviously misunderstood what I said.  I hope the above clarified
for you.

For FIXED moorings especially, the Optimal Spot is where the mooring
(anchor) is set for a particular site (dropoff) is where the boat
is MOST LIKELY to be placed at the dropoff, during the times the
liveaboard boats are MOST LIKELY to be there.

Otherwise, depending on the direction of flow, when a boat is anchored
at the SAME spot, the boat may be 100 meters away from the wall in
blue water;  it may be ALONG the wall (dropoff) in either direction
of the anchor;  or it may be 100 meters AWAY from the dropoff, in the
direction of the shore.

-- Bob.