Timing is Everything


Divers rely heavily on accurate time-keeping. Matt Crowther explains the differences between watch styles and which features to look out for.

It’s easy to spot divers. Whether you’re in the pub or in the middle of a desert you can still suss out who dives and who doesn’t. How? By the watch they’re wearing. Dive watches range from basic analogue styles, that tell the time and probably have a date wheel, to digital models that virtually make you a cup of tea after a dive. And although it can be expensive, a diving watch is often the next piece of diving equipment a new diver buys after a mask, snorkel and fins. With so many makes and models to choose from, including fake dive watches to catch you out, it’s best to know exactly what you need.

The bare essentials

All dive watches need a depth rating of at least 200m. While very few divers see those sort of depths as even a vague possibility, the rating remains important. The designation refers not to realistic depths but to realistic pressures the watch may have to endure when worn by any recreational diver. If 200m is converted into pressure it is roughly the same as

20 atm, and pressures of up to 20 atm can be reached by a diver moving quickly at recreational diving depths. However, many people do dive with watches that are not rated for 20 atm (such as Swatch watches, which are very popular).

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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