Decompression sickness
Decompression sickness can be prevented by decreasing the pressure slowly. This allows the gases which have dissolved in the body to get out in the breathing air without forming bubbles. Divers do this by coming up to the surface slowly, as the pressure depends on the depth, and reducing the depth will reduce the pressure. For each ten metres change of depth the pressure will change by 1 bar, which is about the same as normal air pressure at sea level.