The presence of a combination of several hazards simultaneously is common in diving, and the effect is generally increased risk to the diver, particularly where the occurrence of an incident due to one hazard triggers other hazards with a resulting cascade of incidents. Many diving fatalities are the result of a cascade of incidents overwhelming the diver, who should be able to manage any single reasonably foreseeable incident. Although there are many dangers involved in scuba diving, divers can decrease the risks through proper procedures and appropriate equipment.
As far as fatalities are concerned this is actually the highest risk occurrence. Drowning occurs as a result of preceding problems such as unmanaged stress, cardiac disease, pulmonary barotrauma, unconsciousness from any cause, water aspiration, trauma, environmental hazards, equipment difficulties, inappropriate response to an emergency or failure to manage the gas supply etc. Proper training and the buddy system can go a long way in preventing diver panic and therefore prevents drowning. About twenty percent of diving fatalities are associated with cardiac events, mostly in older divers.
DCS is probably the most common hazard associated with scuba Diving. Decompression sickness is also referred to as the “bends” and can also include symptoms such as itching, rash, joint pain or nausea. When you breathe compressed air at depth, your body tissues will absorb extra nitrogen. When you resurface, if your tissues have absorbed too much nitrogen, the reduction in pressure can cause that nitrogen to create nitrogen bubbles inside your tissues. This is decompression sickness, or the bends. It causes a lot of pain, and, if untreated, and result in nerve and other tissue damage, and even death. Decompression sickness and arterial gas embolism in recreational diving have been associated with specific demographic, environmental, and diving behavioural factors. A statistical study has shown that greater dive depth, past decompression illness, numbers of consecutive days of diving and male biological gender were related to high risk of decompression sickness and arterial gas embolism. While the use of dry suits and nitrox breathing gas, higher frequency of diving in the previous year, higher age, and more years since certification were associated with lower risk, probably as indicators of more extensive training and experience.
An arterial embolism is the blockage of an artery. This can happen to a diver when bubbles form in an artery on ascent and block the blood from flow. Usually, this is the result of pulmonary baro-trauma, or damage to the lungs as a result of differences in the ambient pressure and the pressure in the lungs. For example, if a diver holds his or her breath while ascending, the air inside the lungs will expand and can cause serious or even fatal damage to the lungs.
This is rare but preventable through proper training and careful diving.
Nitrogen narcosis is a feeling of drunkenness or giddiness that divers feel at deeper depths, usually around 80-100 feet in saltwater. While not directly damaging, nitrogen narcosis causes temporary reduction in reasoning, decision making, and motor coordination. This can lead to poor decisions by the diver, resulting in DCS or other problems. Nitrogen narcosis is one of the reasons that diving beyond 60 feet requires additional training after your first certification.
Two basic types of entrapment are significant hazards for scuba divers: Inability to navigate out of an enclosed space, and physical entrapment which prevents the diver from leaving a location. The most common form of physical entrapment is getting snagged on ropes, lines or nets, and use of a cutting implement is the standard method of dealing with the problem. The risk of entanglement can be reduced by careful configuration of equipment to minimise those parts which can easily be snagged, and allow easier disentanglement. Other forms of entrapment such as getting wedged into tight spaces can often be avoided, but must otherwise be dealt with as they happen. The assistance of a buddy may be helpful where possible.