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Chapter 5 — 23
Compass
Possibly one of the least appreciated pieces of equipment, until one needs
it to navigate both underwater and on the surface.
Decompression Meters and Dive Computers (D.C.)
(see Chapter 14)
A decompression meter or dive computer uses a mechanical or electronic model of the inert gas
uptake and elimination by the diver. The dive computers (D.C. or D.C.M.) are based on
decompression theories or algorithms (the principles on which the tables were developed) but often
omit some of the safety factors incorporated in the formal tables. It is impossible for them to exactly
duplicate the very complex gas uptake and elimination from a living diver and to allow for individual
variation. They do however, accommodate the divers need to undertake both repetitive diving and
multi-level diving in a much more manageable manner than the formal decompression tables.
Most current D.C.s also incorporate accurate devices for recording times, depths, ascent rates,
cylinder contents and even water temperatures. Some provide "print-out" capabilities or connections
to a computer. These enable accurate graphical representations of a diver's dive profile, and are
useful to diving physicians treating cases of decompression sickness and to demonstrate where the
diver went wrong. Unfortunately, sometimes it is the dive computer that goes wrong, not the diver.
Communication Systems
The safety of the buddy system of diving depends on the two divers being in constant
communication. Divers who are not in constant communication are in reality only diving in the same
ocean and may or may not be available to assist their buddy in an emergency. Even when they do,
third party rescue is often needed. Buddy lines and buddy diving are discussed in Chapter 34.
Surface detection
aids
The purposes of this class of personal equipment are to:
•
allow the support boat to monitor and find divers on the
surface during or after a dive
•
prevent the diver being struck by boat traffic
•
mark the diver's position when drift diving or while at
the decompression stop
•
help rescue services in lifeboats and helicopters to locate
the diver
•
Fig. 5.23
An inflatable safety sausage or "divers condom".