ISO 6425
ISO 6425 is the international standard a watch must meet to be marked a diver watch. It tests water resistance of at least 100m, a timing bezel, legibility in the dark, and resistance to magnetism, shock, and salt water. Many Seiko Prospex diver references are built to meet it.
At a glance
- Minimum water resistance
- At least 100m
- Qualities tested
- Timing bezel, legibility in the dark, magnetism, shock, and salt water resistance
- Example that meets it
- Seiko Prospex diver references (e.g. the Samurai)
Putting the word diver on a dial or caseback is not a marketing choice: ISO 6425 sets the criteria that label has to stand behind. The standard tests practical qualities that matter underwater, not how rugged a watch looks on the shelf.
What the standard tests
ISO 6425 asks a watch to satisfy a set of conditions together before it can be marked a diver:
- At least 100m of water resistance: the accepted floor for diving
- A timing bezel: a unidirectional ring marked for tracking elapsed time
- Legibility in the dark: hands and markers must be readable without light
- Resistance: to magnetism, shock, and salt water
Why it matters
These requirements separate a real dive watch from a watch that simply carries a depth rating. Seiko Prospex diver references such as the Samurai are among those built to meet the standard.
For concrete picks that take diving seriously, read our guide to the best dive watches under $500.
Examples
The Seiko Prospex Samurai is an example of a diver built to satisfy what ISO 6425 looks for together: at least 100m water resistance, a unidirectional timing bezel, and legibility in the dark.
View this watchSeeing diver on a dial means the watch has passed the standard's conditions, including resistance to magnetism, shock, and salt water.
Comparison
A depth rating alone does not make a watch a diver; ISO 6425 is what draws the line.
| Option A | Option B | Notes |
|---|---|---|
| ISO 6425 diver watch | Watch with only a water resistance rating | The standard requires not just water resistance but a timing bezel, legibility in the dark, and resistance to magnetism, shock, and salt water together. |
Related terms
Watches that show this
Frequently asked questions
What does ISO 6425 require for a watch to be marked a diver?
The standard asks for several conditions together: at least 100m of water resistance, a timing bezel for tracking elapsed time, legibility in the dark, and resistance to magnetism, shock, and salt water. All must be met before a watch can be marked a diver.
Is every 100m water resistant watch an ISO 6425 diver?
No. A water resistance rating is only one of the conditions. ISO 6425 also requires a timing bezel, legibility in the dark, and resistance to magnetism, shock, and salt water; without those a watch is simply water resistant, not eligible to be marked a diver.
Which watches meet the ISO 6425 standard?
Many Seiko Prospex diver references are among the watches built to meet the standard. A model such as the Prospex Samurai brings together the qualities ISO 6425 looks for, from at least 100m of water resistance to a unidirectional timing bezel and legibility in the dark.