NAUI Advanced Scuba Diver
82 Wreck Diving
Since fish and other life is abundant, wrecks are
popular with fishermen, both anglers and commercial
fishers. Expect to encounter fishing line, hooks and even
nets on wrecks. Entanglement in these is possible, but
getting caught is usually not a danger if handled properly.
A sharp knife for cutting line and nets is essential.
The greatest hazards of wreck diving are encountered
when divers enter the interior of sunken vessels. It
is very easy to become disoriented in an unfamiliar maze
of passageways, especially when references are at unusual
angles because of the orientation of the wreck. Darkness,
silt, entanglements, and anxiety compound the problem.
Entrapment is also possible should any part of the wreck
collapse or move while you are inside or underneath it.
There is a great deal you need to know and be able to do
before you can penetrate wrecks underwater.
Two possible hazards for you to keep in mind for
your introductory, non-penetration external survey dive
are sharp edges and losing your bearings. Deterioration
of metal underwater causes it to become thin, sharp,
and jagged. Serious cuts are possible. Heavy gloves are
mandatory. It is easy to become disoriented on a wreck
unless you follow the procedures that will be outlined.
Pay particular attention to this area during your studies
and during your dive.
EQUIPMENT
Your wreck diving gear includes all your regular
gear, such as full instrumentation, an extra second stage
on your regulator, a dive knife, and gloves. Having a dive
light does not qualify you to enter a wreck. It takes additional
equipment, training, experience and practice.
Some additional instruments are needed. Minimally,
these include a depth gauge or dive computer and a
compass. Note that the compass will not perform properly
when on or near a metal wreck. In fact, erratic behavior
by a compass can sometimes indicate that you are close
to a wreck for which you are searching. An underwater
slate is always useful for recording observations and for
communications.
Wreck diving is often done from a boat. The boat
may anchor directly on the wreck or in some instances a
permanent mooring may be in place. In either circumstance,
divers can descend directly to the wreck site using
the anchor line as a down-line (figure 8-4). If there is
current present a “trail line” or “current line” should be
deployed behind the boat to be used by divers who surface
down current from the vessel.
Serious external survey or penetration wreck diving
at the specialty level requires additional specialized
equipment. This gear and its use are covered in the
Wreck Diving Specialty course.
FIGURE 8-4. If your boat is anchored on or near the wreck the anchor line makes a good descent and ascent line for the dive.