Underwater diving emergency

A diving emergency or underwater diving emergency is an emergency that involves an underwater diver. The nature of an emergency requires action to be taken to prevent or avoid death, injury, or serious damage to property or the environment. In the case of diving emergencies, the risk is generally of death or injury to the diver, while diving or in the water before or after diving.

Underwater diving is an activity in which there is a constant risk of an emergency developing. This is a situation common to many human activities. The diver survives in an inherently hostile environment by competence, suitable equipment, vigilance, and attention to detail at a level appropriate to the specific situation. The emergency is the stage of an accident or incident between the causes and the effects, often while it is still possible to take effective action to rectify or mitigate the situation. Like many other classes of emergency, diving emergencies can often be prevented from developing further by appropriate action at an early stage, and by having the appropriate skills and equipment. Professional diving teams are required to have emergence plans in place, and recreational divers are also expected to do so, to the extent appropriate to the dive plan.

An alternative meaning, in the context of medicine, is a medical emergency which was initiated while diving, which may also be described as a diving medical emergency.

Scope and definition

A diving emergency is an emergency experienced by a diver during a dive. This includes the time from when the diver enters the water to dive, until the end of all decompression and the diver has exited the water. Surface decompression may legally be part of a dive. It includes but is not restricted to medical emergencies that are a consequence of diving incidents.

• An emergency is an unexpected and often unforeseen set of circumstances or the consequences thereof that require immediate action, or an urgent requirement for assistance or relief.
• The human activity of underwater diving is the practice of descending below the water's surface to interact with the environment. It is also often referred to as diving, an ambiguous term with several possible meanings, depending on context.

Types and causes

Many circumstances can lead to a diving emergency. Most of them can be mitigated before they become a full emergency,

• Medical emergencies can be the consequence of an emergency with another cause, a health problem, or mismanagement of a routine situation or minor contingency.
• Equipment failures that constitute an emergency are usually failures of life-support equipment, but also can be failures of other equipment that make it difficult, dangerous, or impossible to properly operate safety critical equipment, or to reach a place of safety, such as dive computer lockout or failure with decompression obligation, catastrophic dry-suit flooding, catastrophic loss of buoyancy, loss of insulation in very cold conditions, regulator freeze with free-flow, dislodging of the regulator or full-face mask, helmet comes off the head, roll-off of cylinder valve, or a burst breathing gas hose. Some of these can also be caused by diver or team error.
• Diver errors. such as running out of gas, overstaying at depth and developing a decompression obligation beyond the remaining gas endurance, Losing the guideline under an overhead. Equipment failure due to improper preparation and checks.
• Team errors. emergencies which are the consequences of a person or group involved in the dive, including contracted service providers. eg: Divers left behind at sea, or run over by the dive boat.
• Third party influences. For example dynamic positioning runout, or a diver being hit by a passing boat.
• Environmental problems, situations, effects, or influences such as unforecast weather deterioration, stronger current than anticipated, unexpected low water temperature, silt-out, inadvertent entry into a confined space or overhead environment in low visibility without a guideline to open water, entrapment by nets, lines, wreckage, delta-p situations, collapse of structure, wreckage or overhead, Marine animal injuries, contamination by hazardous materials, surf and currents too strong or mismanaged. Inability to get to exit point due to wind, waves, or currents. Conditions at planned or contingency exit point too rough to exit. Carried away by currents.

Out-of-gas incidents

An out-of-gas emergency occurs when the breathing gas supply is cut off by running out, supply system failure, or supply system interruption. These are the most urgent of the common diving emergencies, and the ones the diver should be equipped and skilled to manage. Many out-of-air emergencies are consequences of other problems that were not effectively managed.

Lost guide line

A lost guide line under an overhead where the exit cannot be seen is a life-threatening emergency, as the diver will die if they cannot find the way out before they run out of breathing gas. The guideline is usually the only sure way of finding the exit in a cave or wreck penetration, and if not found, the probable consequence it that the diver will not get out before their breathing gas runs out, and they drown. The threat is very real, and the urgency increases with time as gas is consumed.

Decompression sickness

• Severe symptomatic decompression sickness

Vertigo and nausea

• Overwhelming vertigo or nausea underwater. This can be caused by motion sickness, barotrauma of the ears, or inner ear decompression sickness. It is likely to cause vomiting, which can compromise the diver's airway and breathing apparatus.

Hypothermia

• Hypothermia developing with a long decompression obligation

Loss of consciousness underwater

• Oxygen toxicity seizure with an unsecured airway.
• Hypoxic loss of consciousness. Hypoxia can be caused to breathing a low oxygen gas mix from the wrong cylinder for the current depth, or a rebreather malfunction. An observant and competent buddy may be able to help.

Inert gas narcosis

• Debilitating inert gas narcosis

Severe hypercapnia

• Severe hypercapnia
• Excessive work of breathing, when extreme, can exceed the capacity of the diver to eliminate carbon dioxide and eventually cause a hypocapnic blackout, which is likely to be followed by asphyxia or drowning. Several mechanisms may cause high work of breathing,such as high gas density, regulator malfunction, loop flood in a rebreather, or excessive exertion with hypercapnia and the cause must be identified before effective action can be taken, but an immediate termination of the dive is generally an appropriate response where possible. A buddy with lower work of breathing may be able to perform a rescue, depending on the cause of the high WoB.

Buoyancy emergencies

• Loss of diving weights, causing inability to maintain depth. If this happens with a significant decompression obligation, the risk of decompression sickness will be high. The CMAS Self-Rescue Diver training includes the use of a ratchet dive reel to control ascent rate in the event of unplanned positive buoyancy at depth due to loss of weights. The end of the line is fastened to a heavy object on the bottom, and deployed under tension to control depth.
• Catastrophic dry suit flooding with severe loss of buoyancy.
• Inability to establish positive buoyancy at the surface.
• Dry suit inversion and blowup with significant decompression obligation. An inverted position in a dry suit causes any excess air in the suit to flow towards the feet, which makes the inverted position stable, and makes it difficult to recover horizontal trim. This is exacerbated if the boots pop off the feet, at which point recovery becomes extremely difficult, if not impossible, If the diver is positively buoyant there may be no way to prevent an uncontrolled buoyant ascent, which will usually occur at an excessive rate, and will generally cause the diver to miss all decompression stops

Entrapment

• Entrapment by entanglement, structural collapse, pressure differential, or water flow. Entrapment prevents the diver from surfacing, and may lead to an out-of-gas emergency, or decompression obligation beyond the capacity of the available gas supply.

Contamination

• Exposure to high risk environmental contaminants. (chemical, biological, radiation etc}

Prevention

See also: Dive planning, Diving safety, and Diver training

The primary goal of dive planning, diver training and diving skills and procedures is to prevent and avoid diving emergencies. A significant part of diving equipment is also used for this purpose, and designed to further this goal. In general diving emergencies are prevented by:

• Reliable equipment, fit for purpose, adequately maintained, and checked for correct function before use. Equipment redundancy is used where necessary to keep risk at an acceptable level, and equipment is designed to keep the risk of accidental misuse low.
• Divers are trained and assessed in the relevant skills, and sufficiently practiced so that they remain competent. Codes of practice, operations manuals, and checklists are used to make effective use of lessons learned from previous experience, and to avoid errors in preparation for a dive. Many of the standard diving skills and procedure are specifically intended to prevent common incidents from developing into emergencies.
• Dives are planned, taking known and suspected hazards into account. Divers and dive teams are briefed on the plans, and the plans are followed. In the majority of dives this is sufficient to ensure that dives are completed without serious mishap. As divers gain experience, their ability to see the early stages of what could develop into a problem improve, and their ability to bring the situation back to a safe state is improved.

Management

See also: emergency management

The diver or diving team should be able to manage a reasonably foreseeable diving emergency with significant risk. This is done by using suitable equipment, and by following procedures developed, tested and known to be as effective in those circumstances. When an unforeseen emergency occurs, the diver, and where relevant, the diving team, must make the best of the situation using the skills, knowledge, intelligence and facilities they have available. Many types of emergency are best avoided simply by not diving in circumstances beyond those in which the diver is known to be competent.

Skills and procedures

See also: Scuba emergency skills, Surface-supplied diving emergency skill, Emergency wet bell procedures, Emergency closed bell procedures, Saturation diving § Emergency procedures, and Hyperbaric evacuation and rescue

Where a hazard cannot be avoided, and the risk is significant, procedures and the relevant skills are developed to manage the problems as they occur, usually at the earliest practicable stage. Where necessary or desirable, equipment which may help manage the foreseen problems may be used, which may require additional skills to operate effectively.

Three levels of skills and procedures are in common use.

• Skills and procedures that are in routine use, which reduce the risk of a problem developing.
• Skills and procedures which are occasionally needed by most divers to manage a relatively rare incident that is foreseeable.
• Skills and procedures that should never be needed, but allow the diver to manage the situation if it does occur, because the consequences are sufficiently serious that competence in the procedures is desirable.

Support personnel

See also: Diving team, Buddy diving, and Solo diving

In most cases the diver has some level of support.

In occupational diving, the diving supervisor is responsible for management of the diving operation, including emergencies. The diver's attendant assists the working diver and supervisor, and the standby diver is specifically employed to be deployed to assist the working diver in an emergency. There may be other team members with specific responsibilities. The dive team is legally required to be competent. The employer or diving contractor is responsible for ensuring competence of all team members, that the equipment is fit for use and the dive plan and emergency plan are appropriate. Dive team members are required to be trained in first aid.

Recreational divers generally only have a dive buddy who may or may not be competent or may even be a further hazard. buddies are either self-selected, or imposed by a service provider who generally requires the divers to sign a waiver releasing the provider from almost all responsibility. However the service provider is usually required to have some level of emergency plan in place for events which are outside the scope of a buddy diver. An alternative to buddy diving is solo diving, where the diver relies on their own resources and skills in any underwater emergency, and equips themself accordingly.

Technical divers tend to be more extensively trained, more aware of hazards and risk, and make their own arrangements accordingly. They are generally not constrained by legislation, but tend to plan by consensus and are more likely to understand the hazards, risks and consequences of a dive plan. Where appropriate they may organise with voluntary support personnel appropriate to the situation.

Emergency plans

In general, there should be plans to deal with reasonably foreseeable emergencies that pose a risk to health and safety wherever there is a duty of care, these may include where relevant:

• First Aid for medical emergencies
• Search and recovery
• Casualty evacuation
• Site evacuation
• Hazmat emergencies

Some of the action generally taken to prepare for possible medical emergencies will include:

• Appropriate first aid equipment available on site
• Adequate oxygen administration equipment available on site
• A plan for evacuation of a casualty to a hyperbaric chamber
• A list of contact numbers, call codes and frequencies for local emergency services.
• How to reach the nearest suitable emergency medical facility from the site.

Where a duty of care exists between an employer and employees or a service provider and clients this may include an obligation to plan to deal with reasonably foreseeable emergencies.

See also

• Buddy diving – Practice of mutual monitoring and assistance between two divers
• Investigation of diving accidents – Forensic investigation of underwater diving accidents
• Diver rescue – Rescue of a distressed or incapacitated diver
• Diving hazards – Agents and situations that pose a threat to the underwater diver
• Diving safety – Risk management of underwater diving activities
• Diving supervisor – Professional diving team leader responsible for safety
• Diving team – Group of people working together to enhance dive safety and achieve a task
• Emergency – Situation requiring urgent intervention
• Emergency response – Appropriate response of emergency services
• Emergency response plan – Action to be taken in specific emergencies
• Public safety diving – Underwater work done by law enforcement, rescue and search and recovery teams
• Rescue diver – Recreational scuba certification emphasising emergency response and diver rescue
• Scuba diving fatalities – Deaths occurring while scuba diving or as a consequence of scuba diving
• Stand-by diver – A member of a dive team who is ready to assist or rescue the working diver
• Underwater search and recovery – Locating and recovering underwater objects