Water Resistance
The water resistance figure on a dial is a laboratory pressure rating, not a real diving depth. 30 metres covers hand washing and rain, 50 metres adds splashes and, for some brands, swimming in shallow water, and 100 metres is what we recommend for regular swimming and the ISO 6425 floor for a certified dive watch. No rating makes a watch safe in a hot shower, bath or sauna, and no watch is truly waterproof; it is only water resistant.
Water resistance is measured under static pressure in a one-time lab test on a new watch, and the swimming you actually do adds only about 5 metres of equivalent dynamic pressure. The figure on the dial reads more optimistic than real life mainly because gaskets age and thermal cycling and impacts erode the seal over the years, not because of large dynamic loads.
What the ratings mean in practice
- 30 metres: hand washing and rain, not swimming
- 50 metres: splashes and, for some brands, swimming in shallow water; not regular swimming or showering
- 100 metres: swimming and snorkelling, and the ISO 6425 minimum for a certified diver's watch
- 200 metres and above: more margin for snorkelling and free diving; for scuba, choose an ISO 6425 dive watch marked DIVER'S, a standard that starts at 100 metres
Gaskets perish over the years
Water resistance relies on the gaskets that seal the case, and those gaskets harden over time. If you really do swim or dive, periodic pressure testing is essential. Always check that a screw-down crown is fully closed before you get in the water.
For more, see the Water and Diving category and the Best Dive Watches Under $500 guide.
Related terms
Watches that show this
Frequently asked questions
Is 100 metres of water resistance enough for diving
For snorkelling, yes; for scuba, the number alone is not enough. 100 metres is the minimum ISO 6425 sets for a diver's watch, but scuba needs a watch that passed all ISO 6425 tests and carries the DIVER'S marking; an ordinary 100-metre watch is a swimming watch.
Can I shower with a 30 metre water resistant watch
It is not advised. 30 metres survives hand washing and rain, but hot water vapour and soap stress the gaskets and raise the risk of a leak over time.
How do I keep the water resistance
Close the screw-down crown before water, have the gaskets pressure-tested every few years, and keep the watch out of hot water and saunas.