One of the most misunderstood ’standards’ of the watchmaking industry is water resistance and how it translates to actual situations you (and your watch) may encounter.  Here’s a brief guide to help make some sense of the system used in rating water resistance and give you some guidelines for choosing the right watch for all of your water related adventures. 

First, it’s important to understand that the ratings associated with watches are derived by testing perfect examples of the watch being rated in a perfectly controlled testing environment (no currents, ideal temperatures, etc.).  It is impossible to duplicate this testing environment in the real world so you need to make some adjustments to allow for all of the variables you are sure to encounter. 

Here are some basic guidelines:

Any watch with a rating of less than 50 meters should not be immersed in water.  These watches offer adequate protection for splashing but aren’t meant for underwater wear. 

Swimming (minimal currents) - A minimum rating of 50 meters

Snorkeling / Open Water Swimming - A minimum rating of 100 meters

SCUBA - A minimum rating of 200 meters

Commercial divers generally use watches rated at 1000 meters which have provisions for the release of helium that may be introduced into the divers environment to avoid air toxicity.  If you aren’t using helium while you’re diving, there’s no benefit to having a helium relief valve.

If your watch is rated in ATMs (atmospheres of pressure) instead of meters, here’s the conversion: while you’re at the surface, you are in 1 ATM of pressure, for every 33 feet you descend, you increase the pressure by 1 ATM.  So at a depth of 33 feet, you are at 2 ATMs and at 66 feet - 3 ATMs and so on.   

Some other things to keep in mind:

• The crown must be locked down / tightened to keep water out of the case.  If you unscrew the crown of a watch rated at 1000 meters, it’s relatively easy to introduce water into the case while washing the dishes!  Always make sure the crown is tight before you get your watch wet. 
• Chronograph pushers should never be activated underwater (a few watches have been designed to allow for the operation of chronograph functions underwater - if you don’t know for sure that your watch is on that list, stick to using the chrono on terra firma only).
• To be water resistant all of the seals/gaskets protecting the case must be in good condition and properly set.  This includes the caseback, crystal, pusher, and crown gaskets.
• Hot water (hot tubs, saunas, etc.) doesn’t do anything good for your watch.
• If you use your watch underwater, you should have the seals/gaskets replaced every year and have it tested for water-resistance at regular intervals.  Many watchmakers are only equipped to pressure test watches to 4 ATMs.  If you intend to use your watch for diving, be sure that your watchmaker tests it to 10 ATMs using both pressure and vacuum tests.
• Whenever your watch comes in contact with seawater, you should rinse it thoroughly with fresh water. 

This entry was posted on Tuesday, April 15th, 2008 at 4:12 pm and is filed under WATCH ARTICLES.
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