People who engage in deep-sea or scuba diving are at risk of a number of injuries, most of which are caused by changes in pressure. These disorders also can affect people who work in underwater tunnels or caissons (watertight enclosures used for construction work). Such structures contain air under high pressure to keep out water.
High pressure under water is caused by the weight of the water above, just as barometric (atmospheric) pressure on land is caused by the weight of the air above. In diving, underwater pressure is often expressed in units of depth (feet or meters) or atmospheres absolute. Pressure in atmospheres absolute includes the weight of the water, which at about 33 feet (10 meters) is 1 atmosphere (14.7 pounds per square inch [1.03 kilograms per square centimeter]), plus the atmospheric pressure at the surface, which is 1 atmosphere. So a diver at a depth of 33 feet is exposed to a total pressure of 2 atmospheres absolute, or twice the atmospheric pressure at the surface. With each additional 33 feet of depth, the pressure increases by 1 atmosphere.
Pressure-related diving disorders can result from
Diving in cold water can rapidly lead to a dangerously low body temperature (hypothermia), which causes clumsiness and poor judgment. Cold water can also rarely trigger fatal heartbeat irregularities in people with coronary artery disease. Other potential diving hazards include
Drugs (prescribed, recreational, and some over-the-counter) and alcohol may have unanticipated, dangerous effects at depth, as can various medical conditions (see table Medical Conditions That May Preclude Diving).
Diving injuries can result in drowning if they cause any of the following:
The Divers Alert Network (www.diversalertnetwork.org; 24-hour emergency hotline, 919-684-9111) is an important resource that addresses the needs of recreational scuba divers around the world in two important ways: