Analogue watches
Many sports watches have bezels and are used to measure elapsed
time, but analogue watches used by divers should have a bezel that
is easy to grip, even with cold, gloved hands. As divers must be
able to monitor exact times to stay within safe diving limits, the
bezel on a diver’s watch should also be unidirectional. A
bezel that rotates only to the left will, if knocked, read a longer
elapsed time, resulting in the diver surfacing early and remaining
within safe limits. Second hands on analogue watches are also important
as they indicate the watch is still working. A watch that stops
while on a dive will give the potentially dangerous impression that
less time has been spent underwater.
Luminous coatings either on the watch face or on the hands are
important for reading information in low light. Tritium coating,
which provides the brightest glow, was banned in Japan due to unacceptable
levels of radioactivity, and was replaced with the safer Promethium,
which is widely used today.
Digital watches
These are becoming more popular with divers, mainly because they
may offer a cheaper alternative to the more traditional analogue.
While digital watches often have various modes, it is most important
that the time display is large and easy to read. The watch should
have a light, and the button that turns it on should be easy to
operate, even with cold hands. Many divers use the stopwatch mode
to count dive time, or set a countdown alarm to indicate the elapse
of a predetermined bottom time.
Diving-related features
The most basic feature that may be included is a maximum depth
indicator. This is useful for logging dives. Some watches have depth
sensors that display current depths as well. Both are often linked
to alarms that are set off if a preset maximum depth limit is broken.
Rapid ascent alarms are another useful feature. When diving with
a computer as well it is worth noting that the alarms may be set
to go off at different rates – always dive according to the
most conservative rate. While dive times are displayed using the
bezel on an analogue watch, digital watches may have a pressure-sensitive
dive timer that switches on automatically when you are just below
the surface and is logged when the dive ends. Temperature displays,
while not so important during a dive, are useful when logging dives.
Some divers use the function to note what suit they need at certain
temperatures.
There are dive watches that have the capacity to log dives. Some
of these models simply log the information as seen on the display.
Others record information that can only be accessed when downloaded
on to a home computer. Dive profiles and information print-outs
are useful for making accurate dive logs that can be stored on a
home computer.
Servicing
All manufacturers recommend that a dive watch is serviced between
every one and two years to check seals and its general condition.
Watches with advanced diving features such as depth sensors may
require fine-tuning to remain accurate. Diving watches should be
serviced at an authorised centre. As they rely on pressure tests
to 200m it is advisable to consult a local dive shop and not a jeweller’s
shop. It is often recommended that the watch is sent back to the
manufacturer.
Straps
The straps on a dive watch need to be long enough to wrap around
a thick wetsuit. Most commonly used are rubber straps, as they are
easily adjusted and cheap to replace. Stainless steel straps should
have two settings, one of which extends the strap to a reasonable
length. Velcro watchstraps popularised by surfers are handy for
divers using many different thicknesses of exposure suit as they
can be set to any length. Velcro or cloth straps are good because
they are threaded through both strap-pins and if one pin breaks
the watch face is still attached. Remember, watchstraps may become
loose when a wetsuit compresses at depth.
Maintenance
Always rinse your watch in fresh water after diving. Keep the bezel
free of sand and debris, and lubricate it with a bit of grease every
now and again. It’s a good idea to take a fresh battery with
you if you are going away. Read the manufacturer’s recommendations
carefully, as your activities and care of the watch may affect the
guarantee or your insurance.
Safety issues
It is important that an additional timing device is carried for
safe diving when using a computer. Dive watches or dive timers provide
back-up information in the event of a computer malfunction. No dive
watches – with the exception of the Suunto Spyder –
carry any decompression information.
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