If you consider that divers rely on a good watch in order not to die, one could expect designated divers watches to be quite robust timepieces. In Germany, where we are based, a divers watch has to fulfill certain criteria before being allowed to be called a divers watch. These watches are usually watertight to a pressure of 20 bar and over. They are also fitted with large indexes and fingers so that they are easy to read through your goggles in the dim light of the deep blue sea at a distance of at least 25 cm. They will also have to have a timer or a bezel which can be turned to indicate the time a diver needs to consider when calculating the remaining oxygen in his or her tank and to keep the intervals needed when ascending back to the surface. This bezel can only be turned one way so as to eliminate the possibility of it being moved by accident, increasing the diving time over the oxygen supply and thus causing a horrible death through drowning.
|housing diameter:||46 mm|
|housing height:||14 mm|
The most robust watch crystals are made out of sapphire glass. Only diamonds and carbide is harder and can scratch sapphire glass. Of course there are other materials such as some metals and stones which will scratch your sapphire glass crystal, so it is not wise to expect the watch to handle any abuse without getting marked. Sapphire has one downside though, it is highly reflective. Some watches receive an anti-glare coating to compensate for this, but sadly this coating is less hard and will scratch more easily.glass
Water tightness or impermeability, surprisingly enough, is the degree to which you can expose your watch to the element water. A watch can be water repellent to a variety of degrees, from surviving the odd splash, to keeping the watch fully functioning long after your crushed body has hit the ocean floor. Please note that these are always theoretical values. Water behaves very differently at different temperatures and with varying salinity. So we took our crayons and made you this rough guide (which, by the way, is in no way legally binding and we will not be held accountable for your watch if you ruin it)::
FYI: 10m is 1 bar is (roughly) 33 ft is (exactly) 0.986923267 atm