For wristwatches, in addition to mechanical damage, external sources of danger can be called a magnetic field, dust and water. Technological progress is taking place by leaps and bounds, it seems that it is not difficult to place the watch movement in an absolutely sealed case. However, not all so simple. The crown and additional buttons require holes in the case, which means that moisture can seep there. Increasing the tightness of the case allowed to significantly extend the service life of wristwatches, so we can say with confidence: water resistance has become a revolution in the watchmaking world and changed a person's life for the better.
Modern manufacturers mark their products with designations containing information on the degree of protection of watches from water. A bit of confusion might arise here. The word "waterproof" by default means absolute tightness. In fact, water resistance is not associated with tightness, but with the level of pressure that the case can withstand without letting water inside.
Currently, the designation standard uses meters and the number of atmospheres as units. Atmospheres, bars show the force of pressure of which water column the watch can withstand (1 atmosphere or 1 bar = 10 meters).
The declared depth on the dial does not mean the permissible immersion depth!
This is because water resistance is measured in a laboratory setting where the watch is held in a static position at a constant temperature. If you add to these conditions the dynamics of the arms when swimming and diving, the pressure on the body will increase. Therefore, it is a mistake to think that in a watch with the designation of 30 meters, you can dive even to a depth of ten meters.
Waterproof classes
10 meters (1 ATM) : The watch is resistant to splashes, raindrops and perspiration.
30 meters (3 ATM) : the watch can withstand splashes, heavy rain, hand washing. If the dial has the inscription WATER RESISTANT, but there is no specific number designation, then their water resistance is 30 meters (3 ATM).
50 meters (5 ATM) : the most controversial class of water protection. Despite the promises of the manufacturers that it is possible to swim fearlessly in a watch marked “Water Resistant 50m”, we do not recommend relying on it completely.
100 meters (10 ATM) : In the watch you can shower, swim and dive without deep diving.
200 meters (20 ATM) : models marked "Water Resistant 200m" are suitable for diving to a depth of 50 meters and staying in the water for no longer than 2 hours.
300 meters and above (30, 50, 100 ATM) : the watch is suitable for deep-sea diving (scuba diving).