Three things are important for the sport scuba diver. They are elapsed bottom time, water depth and the amount of air remaining in your tank. Not knowing this information when diving puts the diver in danger. This is the part of scuba diving that is critical. The laws of nature are unforgiving and a violation is dealt with harshly.

When diving you must keep track of your bottom down time. This can be done using a diver’s watch with a rotating bezel. A good watch is water resistant and rated for 200 feet or 3-4 atmospheres. The watch should be strong enough to take some impart during the dive at depth. Rubber encasement is often important. Luminescent is important to provide easy reading in low light conditions.

Depth gauges tell the diver what water depth they are in. Some gauges are analog and others are digital but they all measure the surrounding water pressure and present it as depth in feet or meters. Depth meters can be attached to your wrist like a watch and like a watch it is important that they can take some impact and are easy to read in low light conditions.

Submersible pressure gauges or SPG’s measure the amount of air remaining in your tank. They are attached to an air hose approximate 20 inches in length. The other end of the hose is attached to the high pressure port on the first stage of your regulator. The gauge can float as you dive or you can attach it to your belt.

There are also devices that combine all three gauges into one unit. You can track your time, depth, remaining air and navigation all though the dive with one device that hangs on your belt.