10 ATM / 100M is a laboratory rating. In daily life, the crown, seals, temperature and age of the watch still matter.
A useful everyday rating
A 10 ATM / 100M rating gives an everyday watch a comfortable margin for rain, hand washing and ordinary contact with water. It is commonly associated with swimming, but actual use should always follow the maker’s instructions and the current condition of the watch. Real-world use adds variables that a laboratory pressure test does not: ageing seals, impacts and the condition of the crown. No engraved number makes damaged seals new again.
The crown must be closed
Kuro uses a screw-down crown. Screw it in fully before the watch meets water, and never operate the crown while the case is wet or submerged. If the watch receives a hard impact, shows condensation under the crystal or has been opened for service, have its water resistance checked before relying on the original rating.
Seals are service parts
Gaskets age. Their condition depends on time, temperature, chemicals and use. Periodic pressure testing is a sensible part of ownership, especially before regular swimming.
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