The diving watch must not only be waterproof, but resistant to the high pressures to which it will be subjected (check for how many pressure atmospheres is guaranteed).
What characterizes a diving watch is to have a movable crown graduated in minutes, the zero of which should be placed in front of the minute hand at the beginning of the dive. The dive time is indicated on the crown by the minute hand.
This crown should only rotate counterclockwise so that it never accidentally indicates a less than actual immersion time. Some models even have a brake to prevent the crown from leaving the position in which it was placed in the beginning of the dive.
Today, with the development of microelectronics, digital watches are increasingly being used, including diving-related functions, including the functions of a profundimeter.
The watch must have very careful conservation. It should be thoroughly washed with fresh water at the end of the dive and, at least once a year, it should be taken to the watchmaker for cleaning, lubrication and replacement of the toric joints and the pile (if necessary), and checked for water tightness.
THE APPEARANCE OF INTERNAL CONDENSATION IN THE GLASS IS A SIGN OF INTERNAL HUMIDITY, SIGN THAT THERE IS ANY WATER INLET, SO IT IS CONVENIENT TO TAKE THE APPLIANCE TO A TECHNICIAN TO BE SEEN
In place of traditional watches, in the early 1980s, electronic diving timers (bottom timer) appeared. These stopwatches have a pressure sensor and start counting the time when the descent starts (at 1m depth), stopping when it hits the surface again. The dive timers have virtually disappeared from the scene with the arrival of digital profundimeters and dive computers.