WHAT DOES WATER RESISTANT REALLY MEAN?
In The Magic of Watches, Louis Nardin says the most important factors [for a watch] are precision, water resistance, and dust and shock resistance.
Water resistance (‘WR’) is your watch’s capability to withstand water, dirt and moisture ingress at specified pressures. High water resistance means high dirt resistance too; even if your dive watch never gets wet, you can reasonably expect its 200m water resistance to give enhanced protection against that other enemy of watches – dust.
Water Resistance Guide
A watch marked with 50 metres on the dial or case back doesn’t mean it can be used diving to a depth of 50 metres. The rating refers to the static pressure it can withstand. The pressure arises when it is moved under water when swimming, the pressure on the watch varies, and can cause seals to fail, and water to enter the watch. Most water resistant watches are not designed for prolonged active use in water.
For swimming and diving, there is a specific range of watches that are clearly marked as 200 – 1000M, which means they are rated for use underwater with additional durability and legibility criteria for use underwater in addition to the water resistance, these watches have a screw down crown.
When using the watch in and around water, do not pull out the crown to change the time, and if the watch has a screw down crown and pushers, ensure these are firmly closed before submerging the watch. Please note, that exposure to water may affect the life span of a leather strap, as such this should be avoided.
Water resistance is stated as a depth ( ATM or Meters ) this means that it has been tested in a laboratory to with stand a static pressure for a short period only at the stated depth. The actual water pressure on the watch during use is greater than the static pressure. During diving into a pool the pressure on the watch is greater at the impact point with the water.
Certain chemicals in water can damage the watch seal as well as perfumes, aerosol sprays and other cosmetics.
Watches should be tested for water resistance every two years and gaskets replaced as necessary to maintain water resistance.
Water Resistance Chart
3 ATM, 30m, 100ft
Suitable for everyday use. Will withstand accidental splashes but not suitable for swimming.
5 ATM, 50m, 165ft
Suitable for everyday use and bathing but not suitable for swimming.
10 ATM, 100m, 330ft
Suitable for everyday use and swimming and snorkelling but NOT suitable for high board diving or sub-aqua diving.
20 ATM, 200m, 660ft
Suitable for all high impact water sports and scuba diving at depths not requiring helium gas. At these depths it is recommended to purchase a professional watch
20 – 50 ATM, 200 – 500m
Suitable for all high impact water sports, scuba diving and saturation diving.
100 ATM, 1000m
Suitable for deep sea diving and intergalactic travels.