PickGlobe
A watch stamped "30 m" is not rated for a dive to 30 metres. That surprises people, and the two sources we read do not even agree on what a 30 m or 50 m rating is for. This guide is for anyone choosing a watch to wear around water who wants to know how much to trust the number.
Quick answer
- Ratings appear as metres, feet or ATM. One repair-shop chart pairs 3 ATM with 30 m, 5 ATM with 50 m, 10 ATM with 100 m and 20 ATM with 200 m.
- Timex lists 30 m as washing hands only. The repair-shop chart lists 30 m as accidental splashes and 50 m as bathing, not swimming.
- Timex says a watch labeled water-resistant with no depth can withstand splashes and rain but should not be submerged.
- The repair-shop watchmaker says to have a watch tested at least once a year if it goes near water.
Where the sources disagree
| Rating | Timex's list (activities that rating allows) | Watch Doctor repair-shop chart (2018) |
|---|---|---|
| 30 m / 3 ATM | Washing hands | Everyday use and accidental splashes, not swimming |
| 50 m / 5 ATM | Adds light swimming | Everyday use and bathing, not swimming |
| 100 m / 10 ATM | Adds snorkelling, poolside diving, surfing | Everyday use, swimming and snorkelling, not high-board or sub-aqua diving |
| 200 m / 20 ATM | Adds recreational scuba diving | High-impact water sports and scuba diving at depths not requiring helium |
The two disagree on 50 m: Timex allows light swimming and the chart says not swimming. Do not average them. Read the maker's own table for the watch you are buying.
What else the sources say
- Timex: do not press any buttons under water unless the watch is indicated as 200 m water-resistant. It also says it only sells water-resistant watches, not waterproof ones.
- The repair-shop chart says its ratings are for a watch in good condition, with gaskets, case-back threads and crown in perfect working order, and that even a small amount of moisture can damage the movement.
What to check before you buy
- The rating printed on the case back or listing, and the maker's own table of what it allows.
- Whether the listing says "water-resistant" with no depth, which Timex treats as splash and rain only.
- Whether you will use buttons or a crown underwater.
- How the seller handles testing and servicing, since the repair-shop watchmaker advises an annual test for watches used near water.
Named standards: trade sources name ISO 22810 for water-resistant watches and ISO 6425 for divers' watches. We have not read the texts, which are paid documents, so we do not describe what they require.
Related guides
Last checked: 21 October 2026. General information, not legal, medical or financial advice. Sources: Timex, water resistance ratings (undated; read 21 October 2026); Watch Doctor, water resistance in watches (blog post dated 22 July 2018; read 21 October 2026).
