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The
degree of water resistance needed in a watch depends entirely on how
it's going to be used. If it won't be immersed to any appreciable
depth, then minimal is fine, but if you're considering it for swimming
or diving, then something more substantial is required.
Depth ratings for the amount of water-resistance vary from about 30
meters (100 feet) to 1000 meters (3300 feet) and more. The point to
remember about them is that the rating determination is done under
controlled conditions in a test lab and rarely reflects the real world.
For instance, in a lab, the watch isn't being moved or bumped, nor is
the water temperature varied.
Generally speaking, a depth rating of less than 100 meters (330') means
the watch can be worn in the rain,
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or will be okay if splashed. Ratings
greater than 100 but less than 200 meters (660') mean the watch can be
used swimming or for shallow dives, like snorkeling. For scuba diving
you need a rating of 200 meters or greater.
Obviously for deep diving, including everything from technical to
commercial or saturation diving, the depth rating should be at the high
end and preferably to an appropriate ISO Standard.
Manufacturers make watches water resistant to varying degrees through
application of sealants inside the case; use of o-rings and gaskets of
rubber or some synthetic material to seal all joints; extra-thick
crystals; extraordinary precision of machined parts; gas filling;
pressure venting; and various other methods.
Many of these features aren't easily discernable, however a couple are
easy enough to observe visually. First is a case-back that screws down
into the case against a rubber or synthetic seal. Look for notches
around the case-back that are the leverage points for the jewelers tool
used for this purpose. Secondly, the crown should screw in against a
similar seal, thus locking down the stem.
Another factor is the case material. For diving, it should be stainless
steel or titanium. Some polymer cases will work if rated to an
appropriate depth. Other materials including gold don't work well
because they aren't rigid enough to withstand pressure at depth. Just a
slight flexing can allow water to seep in around a seal.
Finding a watch that can just get wet is easy enough, but finding one
that can survive the rigors of scuba diving requires more scrutiny. As
mentioned above there are several features that contribute to
maintaining the water-tight integrity of a watch, many of which aren't
so observable.
The
best way to be certain, after visual observation, and a review of the
manufacturers specs, is to choose one with a sufficient depth rating.
If recreational scuba diving is the intended use, then it's reasonable
to infer that a watch with the deeper depth rating of 200 meters (660
feet) or more will meet your needs.
You can read more about finding water resistant watches along with
other articles by John Allen on scuba gear and diving, on his dive
watch site at http://www.mydivewatch.com.
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