What Does Water Resistance on a Watch Actually Mean?

You have probably seen specifications such as 30M, 50M, 100M or 200M water resistant.

It's easy to assume that a watch rated to 30 metres means you can dive 30 metres underwater with it. That isn't the right way to read the rating.

Water resistance is a tested rating

Water-resistance figures describe how a watch performs under defined, static testing conditions. Real life adds factors the test doesn't:

• Movement and water pressure from swimming
• Temperature changes
• Age and condition of the seals
• Impacts and damage

Always follow the manufacturer's instructions for your specific reference.

30M

A 30-metre rating is common on dress watches. Think of it as basic protection against everyday moisture — rain, hand-washing — not as a sign the watch is designed for swimming.

50M

A 50-metre rating provides greater protection, though suitable use still depends on the manufacturer's guidance and the individual design.

100M

A 100-metre-rated sports watch offers far more versatility around water than a basic dress watch — generally suitable for swimming, again subject to the manufacturer's recommendations for that model.

200M

A 200-metre rating is standard across most G-SHOCK models and Citizen's Promaster Dive watches. These are built for regular water use. Dedicated dive watches such as the Promaster Dive also meet the ISO diver's-watch standard, which adds requirements beyond the depth figure alone. Our G-SHOCK buying guide covers the toughest options.

Water resistance can change

Water resistance isn't permanent. Seals can age, dry, compress or become damaged, and the case can be affected by impacts or by operating the crown incorrectly.

If your watch is regularly exposed to water, periodic pressure testing is worthwhile. Our in-house watch services at the North York store include this, and our watch care guide covers the everyday habits that protect it.

The simple rule

Don't buy on the number alone. Think about how you will actually use the watch.

For an office dress watch, high water resistance may not matter. For swimming, travel, outdoor activity and sport, it becomes much more important. For serious diving, choose a watch specifically designed and rated for that purpose.