Watch Water Resistance Explained: What 30 m, 50 m and 100 m Really Mean
The water-resistance figure on the back of a watch is one of the most misunderstood numbers in watchmaking. A watch marked “30 m” is not designed to be taken 30 metres under water, and treating it that way is a common cause of damage. Water damage beyond a watch’s rating is excluded from Titan’s warranty, so it is worth understanding what the numbers mean.
Why the number is not a diving depth
The rating describes the pressure the case withstood in a laboratory test, with the watch held still. In real life, movement adds pressure: a swimming stroke, a dive into a pool or a jet of water from a shower all push water against the seals much harder than still water at the same depth. Temperature changes and ageing seals reduce protection further.
What each rating is suitable for
| Marking | Safe for | Avoid |
|---|---|---|
| Not water resistant | Dry use only | Any contact with water |
| 30 m / 3 ATM / 3 bar | Rain, splashes, washing hands | Showering, swimming |
| 50 m / 5 ATM / 5 bar | Brief immersion, light surface swimming | Diving, water sports |
| 100 m / 10 ATM / 10 bar | Swimming, snorkelling | Scuba diving |
| 200 m and above | Recreational diving (on watches built for it) | Saturation diving unless specified |
As an example, Titan lists its slim Edge watches as water resistant to 30 metres: perfect for the office and the occasional rain shower, but not for the pool.
Everyday habits that let water in
- Hot showers, saunas and steam rooms. Heat makes the rubber seals expand and contract, and steam can get in where liquid water cannot.
- Pressing buttons or pulling the crown under water. This opens a path straight into the case. Operate the watch only when it is dry.
- A crown left pulled out after setting the time. Always push it fully home; if it screws down, screw it in.
- Soap, shampoo, perfume and sunscreen, which slowly attack the seals.
- Old seals. Rubber gaskets harden with age, so a watch that was water resistant when new may not be after several years.
After a battery change or repair
Every time the caseback is opened, the seal is disturbed. If you rely on your watch’s water resistance, ask for the gasket to be checked and the case pressure-tested after any work. Our battery replacement guide covers what else to ask.
What to do if moisture appears under the glass
- Take the watch off and stop using its buttons and crown.
- Do not put it in rice or on a heater; heat can damage the movement and the seals.
- Take it to a service centre as soon as possible. Moisture causes rust within days.
The strap matters too
A water-resistant case on a leather strap is still a bad match for swimming. Leather absorbs water, stretches and can crack. For water activities choose steel, rubber or silicone.
Planning to swim with a smartwatch? Check its rating in the specifications, and read our smartwatch guide before buying.