Divers use different equipment to keep safe underwater. One of these is a depth gauge that is used in tandem with decompression tables and a watch to avoid decompression sickness. A depth gauge is a pressure gauge that displays the equivalent depth in water. It is an essential piece of diving equipment.

A depth gauge and an oxygen analyzer or oxygen sensor can also be used to measure the partial pressure of oxygen or the breathing gas to avoid oxygen toxicity. In the past, older types used a mechanical device and analogue display. Nowadays, most modern diving depth gauges have an electronic mechanism and digital display.