Water resistance on a watch is usually expressed in meters. However, there are plenty of dangerous misconceptions on water resistance on wrist watches. 30m water resistance does not mean that you can dive 30 meters deep with your watch. Well you could, but only once…
Sometimes, a watch doesn’t carry a certain number of meters, and just says ‘water resistant’. Although the term ‘water resistant’ implies that your watch can resist water, it certainly doesn’t.
‘Water resistance’ means that your watch is capable of withstanding accidental splashes of water. Think for example of light rain or washing your hands. The label ‘Water Resistance’ is certainly not capable of surviving being submerged in water. If you try to shower or swim with such a watch, you better rush to a watchmaker.
30m / 100ft/ 3 ATM / 3 BAR
This is one step up. 30m means that your watch can survive accidental splashes, and could survive a shower if the watch is new or the seals are still intact. The rubber seals that keep the water out can wear out quickly, so don’t shower with a 30m watch unless it just came out of the box or had a service recently.
Hot showers are also discouraged, since steam is much more aggressive than water.
50m / 165ft / 5 ATM / 5 BAR
50m means that your watch can be worn in a pool. We are not talking about competitive swimming or sea diving, but sipping mimosas by the water while taking a nap or reading a book.
100m / 330ft / 10 ATM / 10 BAR
A watch with a rating of 100m is suitable for swimming and amateur snorkeling. You can swim and play around in water, but you still have to be careful with aqua diving or high board diving. The impact on the water can still break the seals and allow water inside the watch.
200m / 660ft / 20 ATM / 20 BAR
200m watches can do everything a 100m watch can do, except that these watches are also able to withstand high-impact water sports and higher water pressure.
Your watch is suitable for swimming, high-impact water sports and scuba diving. The case is usually comparable to a 100m watch, but the seals are a lot more robust.
300m / 990ft / 30 ATM 30 BAR or more
These are the watches you must be looking for if you really want to go diving. 300m or more are the only watches who can withstand the immense pressures of saturation diving. That is also why most of these watches have a Helium Escape Valve. Great examples are the Omega Seamaster 300, Breitling Superocean, Bell&Ross 03-92 and Rolex Submariner.