Underwater, whether it's paddling our arms or operating instruments, we need our wrists to turn flexibly, so, the watch needs to be tightly fitted and fixed to our wrists. Although many dive watches are fitted with metal straps, the chemicals in seawater can cause slight corrosion. It is still recommended to replace them with rubber straps that have better water resistance and corrosion resistance in diving. Today some brands have developed canvas or synthetic fiber straps, which are also a good choice.
As the basis for underwater time reading, all dive watches are equipped with eye-catching luminescent hands and scales. Usually, the hands, scales or dials of dive watches are coated with luminescent materials and the size of the hands and scales are deliberately enlarged to make reading the time easier for divers. The early luminescent material was radium, which was discontinued because it contained excessive radioactive elements. The most commonly used luminous material now is Super-LumiNova, which absorbs gamma particles in the light and can last for more than 10 hours (but the intensity of the light will decay after a certain period).
Where is the part of a watch most likely to get water? The answer is definitely the crown, because it is the only part of the watch that connects the outside world to the movement. In order to prevent water from entering the movement through the crown, watchmakers have developed a design called the screw-in crown, which is a water-resistant ring made of rubber added to the crown joint. When the crown is screwed down, water is kept tightly out of the watch (similar to the rubber gasket at the valve of a water pipe at home). There are also many dive watches that have been upgraded so that they not only have larger crowns, but by adding deeper pitting to make them more slip-resistant and convenient to operate underwater.