Be very careful. Watches are often classified by watch manufacturers by their degree of water resistance which, due to the absence of official classification standards uses the following system from from Wikipedia:
Please note the majority of watches will have the level of resistance in metres displayed on the order (please note there is static pressure so 100m does not equal 100m of actual depth in a real life situation).
| Water resistance rating | Suitability | Remarks |
|---|---|---|
| Water Resistant 3 atm or 30 m | Suitable for everyday use. Splash/rain resistant. Not suitable for showering, bathing, swimming, snorkelling, water related work and fishing. | Not suitable for diving. |
| Water Resistant 5 atm or 50 m | Suitable for swimming, white water rafting, non-snorkeling water related work, and fishing. | Not suitable for diving. |
| Water Resistant 10 atm or 100 m | Suitable for recreational surfing, swimming, snorkeling, sailing and water sports. | Not suitable for diving. |
| Water Resistant 20 atm or 200 m | Suitable for professional marine activity, serious surface water sports and skin diving. | Suitable for skin diving. |
| Diver's 100 m | Minimum ISO standard (ISO 6425) for scuba diving at depths not suitable for saturation diving. | Diver's 100 m and 150 m watches are generally old(er) watches. |
| Diver's 200 m or 300 m | Suitable for scuba diving at depths not suitable for saturation diving. | Typical ratings for contemporary diver's watches. |
| Diver's 300+ m for mixed-gas diving | Suitable for saturation diving (helium enriched environment). | Watches designed for mixed-gas diving will have the DIVER’S WATCH xxx M FOR MIXED-GAS DIVING additional marking to point this out. |