The chance of dying while scuba diving is somewhat higher than boxing and over 40 times higher than playing football or water-skiing. Many of the dangers are to do with pressure. The expanding air will need to escape, usually through the mouth or nose, bubbling its way to the surface. The consequences can be life threatening. These two events are known as barotrauma.
Scuba diving is a particular risk for people with asthma.
Some of the typical trigger factors of asthma are present in scuba diving. Use of any other underwater breathing system also carries the same risks. Breathing cool dry air is very irritating to asthmatic airways. Diving gas is dry and when released through a small valve, causes a cooling effect. Thus a diver inhales a cold and dry air mixture which is potentially very dangerous for people with asthma to breathe.