Dive Timer Bezel: Second only to the water-resistance rating, rotating dive timer bezels are an essential part of what makes a dive watch functional. That’s because they give you the ability to set a kind of timer — specifically related to how much oxygen you have in your tank. In use and at a glance, these additions allow you to tell when it is time to resurface prior to running out of oxygen in your tank. They have saved many a life and, without them, a watch is not a true diver. here