Chapter 7- Search and Recovery
Search and Recovery
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tugging on the line. It is important that the line be kept
taut during the sweeps. The amount of area searched
during each sweep depends on the visibility and the size
of the object. There are many variations to the basic circular
sweep, and your instructor will explain the exact
approach you will use in your training. A circular sweep
is the easiest and fastest search method available, but it
does require a search line and good coordination between
the divers involved.
Straight-line searches are used when the exact point
of loss is less well known. The general concept is to sweep
back and forth over an area in a systematic pattern until
the object is located or until the area has been thoroughly
covered. The pattern is usually executed by following
compass headings. Distances for various legs of the patterns
are measured by time or by counting kicks.
A more precise variation of a straight-line search
pattern uses semi-fixed search line to control the searchers’
progress. The line is deployed along the bottom and
its ends are weighted in place at the limits of the search
area. The buddy team then searches along the length of
the line. When they reach an end, that end is moved sideways
a short distance, and the team searches back along
the line. The process is repeated, moving each end of the
line in turn until the object is located or the search area
has been covered. This “jack-stay” or “z” search pattern
is very thorough because there is extensive overlap as the
line is searched back and forth, but it is also time consuming.
It is a good idea to practice a search pattern by
walking through it on land before attempting it underwater.
This way it allows you to discuss the signals and
coordination needed before you submerge and are forced
to rely on slates and hand signals.
After executing a pattern and finding nothing, the
pattern may be repeated by establishing a new starting
point and repeating it. It should minimally overlap part
of the area covered by the previous search. The overlap
increases efficiency and helps prevent any of the search
area from being missed. It should now be rather obvious
why you need to begin at a known point, search a known
area, and finish the search at a known point. Only when
these criteria have been met can a systematic search be
conducted.
It is important that buddy contact be maintained
during searches. There are different ways to accomplish
this depending on the type of search. For circular sweep
searches, buddy contact can be maintained with line pull
signals, but the signals used need to be agreed upon in
advance. During compass course searches, the divers
should swim together with one diver navigating the pattern
and the other doing the searching.
When the object of a search has been located and
the divers need to surface to obtain the lifting equipment,
its position should be marked. It is a good idea if each
member of a dive team has a marker buoy. One can be
used to mark the starting point for a search, and the
other can be used to mark the object once it is located. If
no marker buoy is available, employ the same procedures
for marking a point of loss. Write down pertinent data
before surfacing, and establish ranges and/or bearings
to get a “fix” on the location as quickly as possible upon
surfacing. Also note your location in relation to the buoy
marking the starting point.
If a lift bag is needed, its capacity should approximate
the weight of the object. Lift bags are usually rated
in terms of weight of lift. For example, a 20 kilogram bag
will lift 20 kilograms of weight (50 pound bag will lift 50
pounds of weight). Unfortunately, lift bag capacities are
not divided into very small increments; but fortunately
many bags have “dump valves” for venting excess air
during lifts. As long as control can be maintained by
venting expanding air on ascent using a bag with more
lift than is necessary is acceptable. It is unacceptable to
use a bag that is much too large and which has no provision
to reduce the excess buoyancy.
The next step is to rig the object for lifting. The lift
bag may have a strap and a clip, and this simplifies the
rigging procedure. When possible, place a full wrap or
“round turn” of the strap around the object before securing
the end of the strap rather than simply passing the
strap around the item. You may need to secure the object
to the lift bag with line, and you will need to be able to tie
some appropriate knots (figure 7-8). As a minimum you
should be able to tie: Two Half Hitches or Clove Hitch, a
Bowline, and a Sheet Bend. These knots will be useful for