A small electronic sensor and calculator, carried by the scuba diver, that calculates and displays the basic information needed during a dive, i.e., depth, time, decompression status and tank pressure. By constantly monitoring depth and bottom time, dive computers automatically recalculate the diver's no-decompression status, giving longer dive times while still keeping the diver within a safe envelope of no-decompression time. Computers also monitor ascent rates, logs dives, and measures time intervals between dives.