What is the primary function of a depth gauge in scuba diving?

The primary function of a depth gauge in scuba diving is to measure how deep a diver is underwater. This instrument is essential for divers to understand their depth during a dive, which is critical for several reasons. Depth directly influences the surrounding pressure, the behavior of gases under pressure, and the diver's rate of nitrogen absorption. Monitoring depth helps divers manage their ascent to avoid decompression sickness by allowing them to adhere to safe ascent rates and decompression stops if necessary. Additionally, knowing the depth aids in planning dive time and understanding the effects of pressure on both physiology and equipment.

While other instruments can measure water temperature, calculate dive time, or monitor air supply, these functions are separate and do not fall within the primary purpose of a depth gauge. Its focused role on depth is fundamental to safe diving practices and underwater navigation.