How Do Scuba Divers Determine Depth?

The pressure under water is much higher than above the water. Our body tends to absorb more amount of nitrogen when diving. The more deep we go in the water, the more is the level of nitrogen absorbed. When we come up, the pressure decreases and the nitrogen gas is expelled rapidly out of your tissues in the form of bubbles which can clog your blood circulation. To ensure that you release nitrogen safely, you have to ensure that you do not absorb too much nitrogen in the first place. The "dive planners" helps the divers to know as to know how long they can dive safely at certain depths.  They tell divers how much amount of time they can stay at particular depths. The data table is prepared by the application of gas laws on human bodies, estimations, observations and tests conducted for many years.

In SCUBA (using Self Contained Underwater Breathing Apparatus) diving, air from a tank is breathed using a regulator to enable the diver to receive it at the correct pressure level to offset the effect of surrounding water.  The pressure within the diver's body has to be equal to the surrounding pressure. The scuba diver breathes air under pressure from the aqualung. The acceptable depth of diving depends on the type of the breathing apparatus and the gas with which it is filled.