The Minute Hand 1:02 – Water Resistance

The Minute Hand

Welcome to our ongoing series of short articles about watches which should only take a minute or two to read. We continue today with a brief discussion of water resistance.

Water Resistance

Units of measurement:

  • Meters or abbreviated as "M" - the metric system unit of measure which is about 3.28 feet.
  • Feet or abbreviated as "FT" - the English system unit of measure.
  • ATM - an abbreviation for "Atmospheres". Basically, 1 ATM = 10 M (or roughly 33.8 feet).

The correct term used for watches is "water resistance", not "water proof". The distinction is that at some amount of pressure, any watch will fail to keep water out, so no watch is totally "water proof". There is a liability driven reason to not use the term "water proof". So while watches may not be totally water proof, they are often water resistant to a specified depth.

As an aside, Rolex did produce a special Deepsea Challenge watch for James Cameron which went to the bottom of the ocean in his 2012 expedition. So you can argue that this special watch is "water proof" as there is no greater natural source of water pressure to be found on earth than the Challenger Deep in the Marianas Trench near Guam. Read more about this watch on

The stated water resistance on a watch is the "nominal" or tested depth at which no water enters the watch. However, this is a static test value. Meaning, the watch is motionless in a pressure tank during the test. In actual use (swimming or snorkeling or scuba diving), the movement of your arm through the water will exert additional pressure. So do not assume that you can safely take your watch to the depth marked as you will no doubt move around underwater. So, here are the recommended activities for the most common water resistance values:

  • 30 Meters / 3 ATM / 100 Feet - suitable for an occasional splash, such as washing your hands or getting caught in the rain
  • 50 Meters / 5 ATM / 165 Feet - suitable for swimming
  • 100 Meters / 10 ATM / 330 Feet - suitable for swimming and snorkeling
  • 200 Meters / 20 ATM / 660 Feet - suitable for recreational scuba diving
  • 300 Meters / 30 ATM / 1000 Feet - suitable for most professional diving

Some guidelines about watches and water:

  • Never wind or pull out the crown when the watch is wet or underwater.
  • The maximum water resistance is usually engraved on the case back or may be printed on the dial of a watch.
  • If no water resistance is stated, assume the watch has NO water resistance and avoid getting it wet at all times.
  • Any watch that is regularly immersed in water should be inspected for water resistance ability every year.
  • Watch cases and bracelets should be rinsed thoroughly in fresh water after being in salt water.
  • If you notice condensation in your watch, send it to a qualified watchmaker immediately before rust or corrosion occur.
  • Avoid wearing your watch in saunas and hot tubs as the high temperatures can effect the watch’s gaskets.
  • Avoid bathing or showering with your watch as soap can reduce the surface tension of the gaskets which are designed to keep water out of your watch.

Times up! That's all for today. Stay tuned to the Hawaii Jewelers Association website for the next installment of "The Minute Hand" with your host, Mark Carson of Mark Carson / Individual Design watches.