The rotating bezel on a wristwatch works in several ways, and these include calculating elapsed time for divers, measuring the distance per time unit increments and measuring the distance between a wearer and an event that is seen or heard. Some rotating bezels on wristwatches also work as Greenwich Mean Time indicators, compasses, pulse rate counters and slide rules.
The bezels on dive watches are perhaps the most commonly seen bezels on watches. Dive bezels can either be countdown or count-up timers that tell divers the amount of time they have spent underwater. Tachymeter bezels are seen on chronograph watches and they are used to measure speeds, usually in increments of "one over elapsed time." Telemeter bezels tell the distance of an event that is seen or heard from a wearer's location. Bezels are operated either by rotating the bezel itself or by pressing dedicated buttons for its function.