ISO 22810: 2010 was published in April 2010 by ISO Technical Committee 114 (Horology) to replace the older ISO 2281: 1990. The 1990 standard had become inadequate for two reasons: its terminology was not aligned with international metric pressure usage (atmospheres / bar / metres of water), and its test methods did not address growing consumer concern that water-resistance ratings on consumer watches did not reflect real-world activity (showering, swimming, diving). ISO 22810 tightened both elements: marking conventions and test rigour.
The core test is a static overpressure test. The watch is fully submerged in water and held at the marked overpressure for a defined duration; after the test, the watch must show no leakage (visible water or condensation inside the case). The standard tests each individual watch sold in production (not a sample), so every watch leaving the factory has been tested at its rated overpressure. The test is repeated with the crown unscrewed (where applicable) and the pushers operated (for chronographs).
"30 metres on a watch dial does not mean 30 metres of depth. It means 3 bar of static overpressure in a laboratory tank. Real-world 30 metres in a swimming pool will exceed that pressure on every kick."- Watch industry guide, on the ISO 22810 marking convention
A major terminology requirement is that the rating on the dial or caseback must be expressed as an overpressure value, not a depth in metres. A "100 m" marking is technically shorthand for "10 bar overpressure" or "1 MPa"; the real-world equivalent depth at which a swimmer can safely use the watch is much shallower. The standard explicitly notes that dynamic activity, swimming strokes, jumping into water, knock against pool wall, generates instantaneous pressure peaks far above static depth.
The practical consumer rule the watch industry has converged on (independent of ISO 22810 but compatible with it): 30 m / 3 bar means splash-resistant only (rain, hand-washing); 50 m / 5 bar means short swimming (no diving in); 100 m / 10 bar means extended swimming and snorkelling; 200 m / 20 bar means recreational diving without certification; certified diving requires the separate ISO 6425 divers' standard, which ISO 22810 explicitly does not cover. A 100 m ISO 22810 watch is not a 100 m diver.
ISO 22810 is the baseline standard for non-diver consumer watches across the Swiss, Japanese, German, and Chinese watch industries; almost every modern "water resistant" claim in the consumer market is referenced (explicitly or implicitly) to it. ISO 6425 is the strict superset for actual diving certification: it requires the same static overpressure test plus dynamic shock testing, salt-water resistance, magnetic resistance, antishock, end-of-life-of-strap loading, and a uni-directional rotating bezel with timing graduation. A watch claiming "Diver" or "Diver's" must comply with ISO 6425, not 22810.
A few specific consequences are worth knowing for buyers. (1) A "30 m water resistant" watch should not be worn in the shower; warm water and fast pressure changes degrade gaskets faster than the static test simulates. (2) Water-resistance is not lifetime: gaskets age and harden, so most makers recommend pressure re-testing at every service interval (every 4-7 years). (3) A leak during wear typically appears as inside-crystal condensation under temperature change; this is the cue to send the watch in immediately, before water reaches the movement. ISO 22810 governs the marking, not the lifetime maintenance.
