Water Resistant Watches

If you are considering buying a watch you would be well advised to determine its water resistance rating before you purchase it. Watches always have their water resistance rating on the case, if you are buying online you should find this information in the product specifications. Most of the customers that I speak to do not have a firm grasp of the differences between the ratings in part because of the different ways that the same information is recorded. You are likely to come across these three ways of denoting water resistance; bar, atmosphere or meter. 1 Bar = 1 Atmosphere = 10m.
It is important to remember that unless a watch is a specified professional divers watch it is probably unsuitable for prolonged use in the water. Watches are tested for water resistance in static laboratory conditions for short periods. The result of this is that a 10m rating does not necessarily mean that the watch will endure being taken to that depth, it is merely indicative of the pressure the watch can withstand in still conditions.

Water Resistance Ratings
Some watches have only minimal water resistance, they will be marked simply 'water resistant'. If this is the case then the watch will be splash proof but nothing more, meaning that it should not be worn whilst washing up or showering. If you need a watch that can be used for these everyday tasks it would be better to go with a watch with a water resistance rating of at least 30m. Watches within this category are not suitable for swimming.
The next common rating of water resistance is 50m or 5 atmosphere. These watches are suitable for swimming but not for diving as the pressure at the moment of impact with the water would exceed 5 atmosphere. If you want to do more than just swim you need a watch with a 100m rating. A watch within this classification is appropriate for everyday swimming, watersports and diving, but must not be used for high board or scuba diving.
A watch within the 200m water resistant class can be used for most water sports. If you are searching specifically for a divers watch, it is imperative that you check that the watch complies with international standards for divers watches. Generally the word 'divers' will be imprinted on the case back of the watch. There are higher classifications of water resistance, 300m or more. In principle the higher the water resistance rating the more durable the watch will be, although this is dependant on the quality of manufacture.

Tips for Maintaining Water Resistance
Water resistance can be compromised if the buttons and stem are not screwed down or pressed in correctly. It is also advisable to have your watch pressure tested after the battery is changed, in order to be assured the water resistance has been maintained. The most common way to do this is to return your watch to the manufacturer for the battery change.
Do not immediately worry if your watch has traces of condensation underneath the glass. This can occur during a dramatic temperature change, for example diving in to cold water. Normally the condensation will disperse without any intervention after a number of hours. If it does not I would advise returning your watch to the manufacturer