In 1926, Rolex introduced the Oyster. Thus, the first ‘waterproof’ watch was born. The word ‘waterproof’ for watches was subsequently changed to ‘water resistant’ as nothing in the world is truly absolute. In any case, the water resistance rating is of course related to the case of the watch and its ability to prevent water from entering therefore damaging the movement inside. It does not, however, refer to the water resistance capability of the strap or bracelet of the watch. Unless properly treated, leather straps simply do not like being dipped in water!
The modern watch has several elements with which to allow it to obtain its water resistance rating. A typical dress watch may have a water rating of 30 metres. While this means that the watch should be able to take being submerged in about 100 feet of depth of water and withstand the pressure, this rating of 30 metres actually may just translate to a real world rating of being able to withstand a light drizzle or a quick splash of water. The water resistance rating of a watch should just be taken as a guideline. Another example is the 100 metre water resistance rating. This may mean that you could possibly take the watch for a quick swim in the pool or along with you into the shower. In any case, we should be aware that the only water resistance rating that can be taken at face value is the rating on dive watches
that have been ISO rated. The modern ISO-rated dive watch normally has a minimum of 200 metres of water resistance. One can really expect to dive down to 200 metres with it (although not many of us are actually capable of doing that). So why bother with ISO ratings of more than 200 metres? It means that we appreciate the capability of the watch and that we like our watches to be overbuilt and truly robust to withstand extreme conditions.
How is water resistance achieved in the case of a watch? Firstly, consider the possible points of entry for water into the watch case. Two key zones are potentials here – the crown and the case back. Normally the crown (and possibly the pushers) would have some material like a gasket surrounding the stem. Many implement the screw down crown system to ensure enhanced water tightness here. Some others apply different innovative mechanisms to ensure that the crown has a tight seal when the mechanism is engaged. Also, a gasket is needed around a case back that can be removed. This gasket is impregnable to water once the case back is properly placed into position.
Water resistance is usually indicated on the back case of a watch.
That said, one must now understand the importance of proper watch servicing as during such exercises, the related components of a watch are duly replaced and properly installed. The watch then needs to be tested to ensure that it has retained its expected water resistance rating and prevent any unnecessary damage to the watch.