Decompression sickness, or “the bends”, is an effect of the increased pressure of the air inhaled by scuba divers when swimming underwater at considerable depths. In addition to the pressure exerted by the atmosphere, divers are subjected to additional pressure due to the water above them. Therefore, the air inhaled by a diver while submerged contains gases that exist at higher levels of pressure within the water, and these gases dissolve into the diver’s blood.

As the diver ascends to the surface of the water, the pressure of the water decreases. If the ascent is too rapid, the gases escaping from the diver’s blood may form bubbles that can cause a variety of symptoms ranging from rashes and joint pain to paralysis and death. To avoid decompression sickness, divers must ascend from depths at relatively slow speeds, about 10 or 20 meters per minute, or otherwise make several decompression stops, pausing for several minutes at given depths during the ascent.