Water Resistance
Water resistance is the watch's tested resistance to water ingress, rated in meters or ATM. The rating describes static pressure, not real-world dive depth.
A watch's water resistance rating is the static pressure at which its seals were tested to remain watertight. It is expressed in meters (e.g. 100m), feet, or atmospheres (1 ATM ≈ 10m). The rating is a pressure equivalent, not an operating-depth recommendation — a 30m-rated watch is splash-resistant only, not for showering or swimming, because real-world activity (swimming strokes, dive impacts, water-jet pressure) generates dynamic pressure far higher than the static rating.
Industry rules of thumb: - **30m / 3 ATM**: splash-only. Don't shower with it. - **50m / 5 ATM**: light swimming, no diving. - **100m / 10 ATM**: swimming, snorkelling. - **200m / 20 ATM**: recreational scuba diving. - **300m+ / 30 ATM**: professional-grade dive watches; meets or exceeds ISO 6425.
ISO 6425 is the international standard for dive watches and requires not just static pressure but also additional tests (immersion at 1.25× rated depth, thermal shock, magnetism, salt water exposure). A watch can be "300m water-resistant" without being ISO 6425 certified.
Common questions
Can I shower with a 30m water-resistant watch?
No. 30m / 3 ATM is splash-only — designed for hand-washing rain. Hot showers add thermal stress to the seals and the water-jet impact pressure is far higher than static 30m. Shower-safe watches are typically rated 100m or higher.
What's the difference between 'water resistant' and 'dive watch'?
Water resistance is a rating (a number of meters). A dive watch is a specific category that meets ISO 6425 — at minimum 100m water resistance plus a unidirectional bezel, lume, magnetism resistance, and shock resistance. Most are rated 200m or more.