NAUI Advanced Scuba Diver
58 Introduction to Deeper Diving
most people realize, so monitor your progress by watching
your depth gauge and counting slowly or comparing
your ascent to elapsed time. You should stop at 5 meters
(15 feet) to decompress for a minimum of three minutes,
even if your total dive time is well under the no-decompression
limits. This is a good safety precaution.
It is good practice, also, in the event that a mandatory
decompression stop should ever be required. Maintain
yourself at the decompression stop level and keep activity
to a minimum. Sometimes a weighted bar, called a
“decompression bar” or “deco bar,” is used to provide a
better base for decompression than the down line. The
decompression bar can accommodate more divers than
a down line, and its use is common practice for charter
dive boats.
In order to relocate the down line for your ascent,
you will need to dive nearby, or you will need to navigate
accurately. It is best to stay close to and in sight of the
ascent line. If you are unable to locate the down line for
your ascent, you will have to perform a hovering safety
stop and surface without the reference and control provided
by the line. This could be hazardous under conditions
that warranted the use of a vertical descent/ascent
line. If a deep dive is being made from shore, you may be
able to swim toward shore and make your safety decompression
stop on the bottom in shallow water. Deep dives
from shore also allow you to follow the contour of the
bottom for descents and ascents, but result in less time
at depth because the angled descent requires more time
than a vertical descent on a down line.
When a dive has very short bottom time, such as a
quick dive to free a fouled anchor, the dive is termed a
“bounce dive.” Such dives can increase the chances of
decompression sickness occurring and are to be avoided,
especially following a deep dive or any dive approaching
the no-decompression limits. It is better to spend one,
continuous length of time at a depth than it is to spend
an equal amount of time at that depth with a couple of
trips to the surface included.
Upon surfacing from the water after completion of
your precautionary decompression stop, note the time
for the start of your surface interval, signal the surface
support person that you are “OK,” and make your way
to the exit. After exiting the water and removing your
gear, take it easy for a while. Avoid exertion, hot showers,
alcohol, and drinks containing caffeine. You should
also wait at least 12 hours, longer if your dive is one of a
series of repetitive dives, before flying in an airplane. Any
hard work, such as pulling the anchor or carrying heavy
equipment, should be performed by people who were not
involved in the dive.
Perhaps you feel that with all of this knowledge and
with the experience of a couple of dives beyond 18 meters
(60 feet) you are ready to handle any kind of deep dive.
There is much more you need to know. Your deep diving
ability as an Advanced Scuba Diver is limited to the depth
of your training. Gradually increase your depths to stay
within your comfort envelope and multi-tasking ability.
Plan to obtain additional training if you are interested in
deep diving or have a need to make dives to deeper depths.
Before you rush off to make deep dives on your own,
remember all of the equipment you need in order to make
deep dives and remember your responsibility to the diving
community to conduct your recreational dives safely.
OVERVIEW OF A TYPICAL
INTRODUCTORY DIVE
The planning and preparation for your introductory
dive may be assigned to you. As you set up and prepare
for the dive, you do so under the supervision and direction
of your instructor. Equipment such as the down line
and the hang-tank is provided, but you may be required
to prepare it for use. A review of the NAUI Dive Tables is
usually included, and may be part of the briefing for the
dive. A more thorough review and additional information
on dive tables theory and usage is included in the NAUI
Master Scuba Diver course. The briefing will also include
instructions on activities for the dive, which may involve
recording the readings of depth gauges for comparison,
noting the effects of pressure on various items, buoyancy
loss measurements, an aquatic life survey, a guided tour,
or a combination of these. A precautionary decompression
stop will be included, and you may have the opportunity
to practice additional precautionary decompression