Dive watches: what makes one, ratings explained, and how to use the bezel
A dive watch is a watch built to be worn underwater. Under the international standard ISO 6425, it must be water-resistant to at least 100 m (tested to 125% of its rating), have a way to time a dive (usually a one-way rotating bezel), be readable at 25 cm in total darkness, and show clearly that it's running. Most modern dive watches are rated 200 or 300 m.
Try a dive bezel
Bezel not set
Press Start dive: the bezel's triangle lines up with the minute hand, and you read elapsed minutes where the minute hand points on the bezel, just as divers do.
A learning tool, not a dive computer. Plan dives with your training, a dive computer and tables.
What makes a watch a dive watch
| ISO 6425 requirement | Why it matters |
|---|---|
| Water resistance of at least 100 m, each watch tested to 125% of its rating | Safety margin: a 200 m watch is tested at the pressure of 250 m |
| A preset elapsed-time indicator, usually a unidirectional bezel | A bump can only turn it the "safe" way, making the dive look longer, never shorter |
| Legible at 25 cm in darkness | Luminous hands and markers you can read at depth |
| A visible sign that it's running (usually a lumed seconds hand) | You can tell at a glance the watch hasn't stopped |
| Resistance to shock, magnetism, salt water and temperature changes | Real-world diving conditions |
| A strong strap or bracelet and secure attachment | So the watch isn't lost underwater |
Watches certified to the standard may print "DIVER'S 200M" on the dial. Many watches that look like dive watches are not certified.
What water resistance ratings really mean
| Rating | Good for |
|---|---|
| 30 m / 3 bar / 3 ATM | Rain, splashes and hand washing. Not swimming. |
| 50 m / 5 bar | Light swimming in a pool. |
| 100 m / 10 bar | Swimming and snorkeling; the minimum for an ISO dive watch. |
| 200 m / 20 bar | Recreational scuba diving. |
| 300 m and up | Professional and technical diving. |
| Helium escape valve | Saturation divers who live in pressurized chambers; it lets helium out during decompression so the crystal doesn't pop off. |
The rating comes from a lab pressure test, not a depth you can safely take any watch to. Screw down the crown before swimming, never press chronograph pushers underwater unless the watch allows it, and have the seals checked every few years.
How to time a dive with the bezel
- At the start of the dive, turn the bezel so its triangle (the zero marker) lines up with the minute hand.
- During the dive, read elapsed time where the minute hand points on the bezel: pointing at 20 means 20 minutes.
- The bezel turns only counterclockwise, so an accidental knock can only make it show more time underwater, never less.
The same trick times anything up to an hour: parking meters, cooking, laundry. Or use the online timer.
Dive watch history
| Year | Watch | Why it matters |
|---|---|---|
| 1926 | Rolex Oyster | A screw-down case and crown, the first commercially successful waterproof wristwatch |
| 1932 | Omega Marine | An early wristwatch designed for diving |
| 1953 | Blancpain Fifty Fathoms | Built for French navy combat divers; set the modern dive watch template |
| 1953 | Rolex Submariner | Rated to 100 m; the most copied dive watch design |
| 1957 | Omega Seamaster 300 | Omega's first professional dive watch |
| 1965 | Seiko 62MAS | Japan's first dive watch |
| 1967 | Doxa SUB 300 and Rolex Sea-Dweller | The orange-dial SUB; the Sea-Dweller soon added a helium escape valve for saturation divers |
| 1982 | ISO 6425 | The international dive watch standard is published |
| 2012 | Rolex Deepsea Challenge (experimental) | Strapped to James Cameron's submersible to the bottom of the Mariana Trench, about 10,900 m |
| 2022 | Rolex Deepsea Challenge | Rated to 11,000 m, the deepest rating of any production watch; tested to 13,750 m |
Dive watch vs. dive computer
A dive watch keeps time and tracks elapsed minutes. A dive computer measures depth and calculates decompression limits, and is what most recreational divers rely on today. Many divers wear both, with the watch as a backup. See every watch style in types of watches A to Z and the brands behind them in watch brands A to Z.
Questions people ask
What is a dive watch?
A watch designed to be worn underwater. Under ISO 6425 it must be water-resistant to at least 100 m, have an elapsed-time indicator such as a one-way rotating bezel, be readable at 25 cm in the dark, and show that it is running.
Can I swim with a 30 m water-resistant watch?
Not recommended. 30 m (3 ATM) means splash-resistant only. Choose at least 100 m for swimming.
Why does a dive bezel only turn one way?
So an accidental knock can only make it show more elapsed time, which is the safe direction, never less.
What is a helium escape valve?
A one-way valve for saturation divers. Helium seeps into the watch in pressurized chambers, and the valve releases it during decompression so the crystal isn't forced off.
What is the deepest-rated dive watch?
The Rolex Deepsea Challenge (2022), rated to 11,000 m and tested to 13,750 m.
Do divers still use dive watches?
Most rely on dive computers, but many wear a dive watch as a backup timer.
Sources
- Aquastar: what is ISO 6425?
- ISO 6425:2018 Divers' watches
- WatchesBySJX: Rolex Deepsea Challenge 11,000 m
Last updated October 22, 2026. Found an error? Tell us.