WATER RESISTANCE RATINGS

"Water resistant" is a common mark stamped on the back of wristwatches to indicate how well a timepiece is sealed against the ingress of water. It is usually accompanied by an indication of the static test pressure that a newly manufactured watch was exposed to in a leakage test.

An indication of the test pressure in terms of water depth does not mean that a water resistant watch was designed for repeated long-term use in such water depths. For example, a watch marked 30 meters water resistant cannot be expected to withstand activity for longer time periods in a swimming pool, let alone continue to function at 30 meters under water. This is because the test is conducted only once using static pressure on a sample of newly-manufactured watches.

The test for qualifying a diving watch for repeated usage in superior depth ratings include added safety margins to take factors into account like aging of the seals, the properties of water and seawater, rapidly changing water pressure and temperature, as well as dynamic mechanical stresses encountered by a watch in the underwater environment.