Read more Features Rotating Bezel A rotating bezel is a circular piece around the crystal of a watch capable of rotating in one direction with markings at each five-minute interval. Its main purpose is to mark the passage of a specific amount of elapsed time under an hour. For divers, its utility helps to monitor the breathing time they have remaining under water; Since the bezel is unidirectional, if a rock hits it, the bezel will only rotate in the elapsed direction, which protects against miscalculating the time left in your dive. Deployant Clasp Sometimes referred to as a divers clasp, is an expanding metal mechanism composed of surgical grade steel, designed to fasten the watch bracelet for the perfect fit. Luminous Fill The hands and indices of the watch dial are coated with luminescent materials - a radioactive alpha emitter, which help the dial glow for a short time after being exposed to light. The alpha particles of the luminescent coating are made to excite a fluorescent material, which glows; Since even a single sheet of paper easily blocks alpha particles, there is no significant radation exposure and no need to worry. Screw-Down Crown Commonly found on dive watches, a screw-down crown ensures water-resistance by sealing the crown to the case of the watch. The screw down crown is not operated like a traditional push/pull crown, rather, it is accessed by pushing the crown downward and unscrewing it. An airtight seal is created when the case locks with the crown's internal threads, fastening the crown securely into place. Read more Read more Read more Read more