Abstract: A dive timer for divers which automatically begins measuring bottom time after detecting submergence below a predetermined depth and, upon resurfacing, automatically stores the measured bottom time in memory and begins measuring the surface time following the dive. The current bottom time and current surface time are alternatively displayed during their respective time intervals, and bottom times and surface times from previous dives may be recalled from memory for display. The apparatus incrementally numbers dives, and stores and displays a particular bottom time and surface time with the dive number associated therewith. Bottom times and surface times are recalled from memory in the reverse sequence to that in which they were measured. Additionally, circuitry is disclosed for measuring and displaying time of day and calendar information, and for operating the apparatus as a stop watch and an alarm.