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MASK , SNORKEL, and FINS : |
 Sometimes
called your "basic" gear, these three cover the minimum
"adaptations" you need as a diver: seeing, breathing
and swimming with your legs instead of your arms. When you put
on scuba gear, you still need the mask so you can see and the
fins for swimming. You still use the snorkel to save air at
the surface, or in case you have to make a long swim (planned
or unplanned) with an empty cylinder, especially if there's
a current or chop. Except in a few instances, the snorkel is
considered required recreational scuba equipment even though
you can breathe from your scuba system.
In technical diving,
you usually omit the snorkel because it causes more problems
than it solves. However, tech divers do equip with snorkels
in some circumstances, such as if they may end up a long way
from a boat and have to wait for it to pick them up.
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EXPOSURE PROTECTION: |
 You'll
want an exposure suit of some kind on all dives to protect you
from heat loss and from abrasion. As covered in Chapter Four,
water conducts heat from your body about 20times faster than
air at the same temperature. Because of this, you can become
dangerously chilled in water temperatures that would be comfortable
in air. In very warm water you may not need thermal protection,
but you still benefit by wearing something to protect you from
incidental scrapes and stings.
Exposure suits include lightweight
body suits (a.k.a. skin suits), wet suits and dry suits. You
use body suits in warm water primarily for abrasion protection.
Wet suits provide more insulation, making them suited to longer
dives in warm water as well as cooler water diving. Dry suits
provide the most insulation, enabling you to dive in cold
waters, including at the Arctic or Antarctic. Besides suits,
you'll usually wear some form of hand and foot protection,
and in cooler water, a hood. Because tech dives can be two
or three times longer than recreational dives, tech divers
generally wear more insulation (almost never body suits) compared
to recreational divers for the same temperature water. |
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WEIGHT SYSTEM: |
 Exposure
suits are buoyant, and you may be, too, depending upon your
physical characteristics. When diving, you use a weight system
to just offset any buoyancy, thereby letting you swim gently
downward. You don't wear so much weight that you sink rapidly.
Weight systems may be a belt, a harness or integrated into your
BCD. In recreational diving, a weight system must have a quick
release by which you can jettison your weight with one hand
- just in case you end up in a situation in which you want to
be sure you stay at the surface. You may need a weight system
in tech diving, but frequently you do not. Tech gear may be
so extensive and heavy that there's no need for any weight system
at all, even with a very buoyant exposure suit. If you need
weight on a technical decompression dive, the dangers caused
by losing it may be higher than any difficulty jettisoning them.
For this reason, tech divers commonly have a weight system that
requires operating more than one release to get rid of the weight. |
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SCUBA SYSTEM : |
| The standard recreational scuba system consists
of three integrated components a high pressure compressed gas
cylinder, a regulator and a Buoyancy Control Device (BCD). Each
of these has subcomponents. |
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HIGH PRESSURE COMPRESSED GAS CYLINDER: |
 This
is a steel or aluminium cylinder than holds air (or enriched
air) typically at a full pressure that ranges from 150 bar/2250
psi to 200 bar/3000 psi. You typically wear a single cylinder
in recreational diving. Tech divers typically wear double, high
capacity cylinders joined by a special valve (manifold). |
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REGULATOR: |
 Your
regulator delivers air from your cylinder on demand when you
inhale. It does this by reducing the compressed air pressure
to the match the surrounding water pressure in two steps or
stages. Your regulator also has an alternate air source for
sharing with a buddy in an emergency and an SPG (submersible
pressure gauge) so you know how much air you have at all times.
A third hose, call the LPI (low pressure inhalator) supplies
air to your BCD.
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BCD (Buoyancy Control Device): |
 Your
BCD is an inflatable jacket that you wear. It holds your scuba
system together and allows you to control your buoyancy by adding
or releasing air. By inflating or deflating the BCD, you can
float easily at the surface or swim effortlessly over the bottom.
Your BCD may also include your weight system. Tech divers use
a similar scuba system, but with some important differences.
The tech diver has two completely independent regulators and
uses a wing-type BCD with a separate harness. The wing-type
BCD sandwiches between the cylinders and the harness; tech BCDs
may have two independent bladders and inflation/deflation systems. |
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INSTRUMENTATION: |
 Besides
needing to know how much air you have, you also need to know
how long you've been underwater and your depth to avoid decompression
sickness. At the minimum, you'll need an underwater timer or
watch and a depth gauge, though it is more common to use a dive
computer. Dive computers help you avoid decompression sickness
by applying time and depth information to a decompression model.
In addition, you use an underwater compass to assist finding
your way.
In tech diving you need the same instruments,
but you always have two timing devices and two depth gauges
- typically dive computers. In recreational diving you may
opt to mount your instruments into a console, but in tech
diving you wear instruments on your wrist.
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KNIEF / CUTTING TOOL: |
 Although
it isn't common to get entangled, it does happen, so having
a cutting tool of some kind is standard equipment (except where
prohibited by law). The typical choice is a dive knife, though
you may prefer special shears and other cutting devices. In
tech diving you go one step further, always having two cutting
tools, one of which you can reach with either hand. |
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SIGNALING DEVICES: |
 In
many situations, you can be hard to see if you surface a long
way from the boat due to currents or a dive plan error. Audible
and visual signaling devices attract the attention of boat crew
or other divers for pickup or emergency assistance.
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DIVE TABLES / PLANNERS: |
 As
a recreational diver, you always stay within depth and time
constraints that allow you to swim directly to the surface at
any time should the need arise. Although you use a dive computer
to help you stay within these limits, you use dive tables to
plan your dive and as a backup in case your computer malfunctions.
The Recreational Dive Planner (RDP) is by far the most popular
table for this, though you can choose from others, such as the
US Navy tables (which you can find laid out in different ways
for convenient use). You use underwater slates to carry dive
plan information, as well as to communicate. Tech divers make
dives with required decompression stops at specific depths and
times. You would use somewhat more sophisticated dive computers
to determine these depths when tech diving, but you still need
dive tables for planning the dive and to consult in case of
a computer problem. Rather than use pre-printed tables like
the RDP, in tech diving you create custom dive tables for a
specific dive using desktop decompression software. |
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DIVE LOG BOOK: |
 Your
certification cards establish your training qualifications,
but it's your log book that tells what you've done with those
qualifications. By keeping a log book, you create a tangible
record of your dive experience, which some resorts and live-aboards
will want to see. As you move up through the diver training
ranks, you'll need your log book to establish that you meet
experience minimums required by many courses. The typical log
book is on paper, though you can get computer programs that
log your dive. If you prefer to log your dives in a computer,
you'll carry printouts that summarize your experience. |
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