All computers have a few features in common, they are primarily either wrist-mounted or gauge mounted. All computers will display your current depth, and No Decompression Limit (NDL), and you will have access to maximum depth, current time, and total elapsed dive time. Many of them will also include temperature and a stopwatch in the display. Most also have built-in alarms as warnings for low NDL, ascent rate warning and bottom time/maximum depth. Some have the ability to compute Nitrox dives – it you are a Nitrox diver, you are going to want to look for a computer that states it is Nitrox capable.