I�m advanced Padi diver and I�ve had this watch for about five years now and its been on several dives with me my deepest was in Egypt 50mtrs it�s a great watch the info you want: A bezel is a rotating dial on the face of your dive watch with a pointer indicator. When you are ready to descend, you align the bezel with the minute hand, where it stays for the duration of the dive. By comparing the bezel and the minute hand you can easily see how long you have been submerged. Note about the rotating bezel on a good dive watch: it will only turn counterclockwise! Since it is possible to knock your watch against your body or have it turn by accident. As for the screw on the left-hand side this is for Helium escape valve why helium escape valve? Air cannot be used for deep-sea dives, since nitrogen (a constituent element of air) becomes toxic at a depth of 60 metres.Therefore, when carrying out work at great depths, professional divers stay in a diving bell for several days breathing a mixture of gases containing a high proportion of helium. The pressure is gradually increased to reach the pressure at the working depth. The divers, still inside the bell, are then lowered to the working site. They leave the bell to carry out their work. Once their work is complete, they re-enter the bell, which is then raised to the surface. Pressure is then returned to atmospheric levels and this is when the valve must be opened (only for deep-sea dives lasting several days). You can download a instruction manual at the omega website www.omegawatches.com hope this helps