The manufacturers indicate mostly the degree of waterproofness in metres (m), feet (ft) or atmospheres (atm).
Watches with the "waterproof" name, with or without indication of overpressure, have to be complied and have to undergo successfully the tests planned in the standard ISO-2281.
These watches are intended for a current daily use and have to resist to the water during exercises such as the short-term swimming.
The watchmaker company "Alcide Droz & Sons", established in St-Imier (Bern) since 1864, developed the first watch attested waterproof.
[1] This pocket watch is nowadays on display at the International Watchmaking Museum in La Chaux-de-Fonds.