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Watch water resistance ratings are one of the most misunderstood specifications in the industry. The numbers on your dial — 30m, 100m, 200m, 300m — do not mean what most people think they mean. Here’s the definitive guide.
What Water Resistance Ratings Actually Mean
Water resistance ratings are tested under static laboratory conditions, not dynamic real-world use. The rating represents the pressure the watch can withstand — but physical activity significantly increases water pressure on a watch case.
- 30m (3 ATM): Splash resistant only. Do not swim, shower, or submerge. Rain is borderline acceptable.
- 50m (5 ATM): Light swimming acceptable. No diving, no showering with force.
- 100m (10 ATM): Swimming acceptable. Light snorkeling possible. Recreational diving not recommended.
- 200m (20 ATM): Swimming, snorkeling, recreational diving acceptable. Not for technical scuba diving.
- 300m (30 ATM): Professional diving suitable. Rolex Submariner rating. Safe for recreational scuba.
- 600m-1,000m+: Professional saturation diving. Omega Planet Ocean, Rolex Sea-Dweller territory.
Factors That Affect Water Resistance
Water resistance degrades over time as gaskets age and dry out. Annual testing (free at many watch service centers) is recommended for watches regularly worn in water. Impact forces (diving into water) dramatically increase pressure beyond the theoretical static rating.
Maintaining Water Resistance
Have gaskets replaced at every service. Never open the crown while wet. After saltwater exposure, rinse the watch with fresh water. Screw down the crown fully before any water exposure.
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