Water Resistance Explained: ATM, Metres and What You Can Actually Do

Few watch specs are as misunderstood as water resistance. A watch marked “30m” is not safe to swim in 30 metres of water — the ratings come from static laboratory pressure tests, not real-world depth. Here is what the numbers actually mean, so you can wear your watch with confidence.

The ratings, in plain English

• 30m / 3 ATM — Splash-resistant. Fine for rain and hand-washing. Not for swimming.
• 50m / 5 ATM — Survives a quick swim or shower, but not diving or watersports.
• 100m / 10 ATM — Genuine swimming and snorkelling. The sensible everyday minimum for a watch you want to stop worrying about.
• 200m / 20 ATM — Recreational scuba diving and all watersports.
• 300m+ / 30 ATM+ — Serious dive watches, built with screw-down crowns and reinforced cases.

Why the numbers feel high

The pressure used in testing is applied evenly and without movement. In real life, swimming, diving off a board, or a strong current creates sudden pressure spikes far higher than your static depth. The generous-looking rating is the engineering safety margin — which is exactly why you should treat 100m as the threshold for comfortable swimming, not 30m.

Three rules that protect any watch

• Never pull out the crown or use chronograph pushers while the watch is wet or submerged.
• If your watch has a screw-down crown, make sure it is fully tightened before water contact.
• Rinse with fresh water after the sea or a chlorinated pool, and dry gently.

Keep it sealed

The rubber gaskets that keep water out harden and shrink over time. If you regularly swim with your watch, have its seals tested every 18–24 months. Across the AURENCOURT collection, each reference states its true water rating plainly on the specification table — from everyday splash-resistant dress pieces to 300m dive-ready tool watches — so you always know exactly what you are wearing.