Diver rescue, usually following an accident, is the process of avoiding or limiting further exposure to diving hazards and bringing a diver to a place of safety. A safe place generally means a place where the diver cannot drown, such as a boat or dry land, where first aid can be administered and from which professional medical treatment can be sought. In the context of surface supplied diving, the place of safety for a diver with a decompression obligation is often the diving bell.
Rescue may be needed for various reasons where the diver becomes unable to manage an emergency, and there are several stages to a rescue, starting with recognising that a rescue is needed. In some cases the dive buddy identifies the need by personal observation, but in the more general case identification of the need is followed by locating the casualty. The most common and urgent diving emergencies involve loss of breathing gas, and the provision of emergency gas is the usual response. On other occasions the diver may be trapped and must be released by the rescuer. These first responses are usually followed by recovery of the distressed diver, who may be unconscious, to a place of safety with a secure supply of breathing gas, and following rescue, it may be necessary to evacuate the casualty to a place where further treatment is possible.
Recommended procedures for recovering a disabled or unresponsive scuba diver to the surface have varied over time, and to some extent depend on circumstances and the equipment in use. None are guaranteed to be successful.
In all rescue operations, the rescuer must take care of their own safety and avoid becoming another casualty. In professional diving the supervisor is responsible for initiating rescue procedures, and for ensuring the safety of the dive team. The rescue is generally carried out by the stand-by diver, and for this reason the stand-by diver must be willing and competent to perform any reasonably foreseeable rescue that may be required for a planned diving operation. A similar level of competence is desirable, but not required of recreational divers, who generally have a poorly defined duty of care to other divers, and are usually only trained in rescue and first aid as optional specialties. Nevertheless, recreational divers are usually advised by their training agencies to dive as buddy pairs so they can assist each other if one gets into difficulty.
Reasons for needing rescue There are many reasons why a diver may need rescue. These generally imply that the diver is no longer capable of managing the situation. Scenarios requiring rescue include: running out of breathing gas inability to access the breathing gas due to an equipment failure unconsciousness or incapacitation due to trauma, diving disorder, hypothermia, narcosis, fatigue, or other medical condition inability to see the depth gauge or diving computer to make a safe ascent, generally because the diving mask is lost, keeps flooding or is damaged panic, or inappropriate response to a problem becoming overwhelmed by unexpected environmental conditions becoming lost or trapped underwater inability to control buoyancy and/or inability to apply thrust sufficiently to ascend (in Scuba diving without a lifeline) inability to return to the shore or a boat after a dive The diver may get into a situation requiring rescue through incompetence, unfitness or bad luck.
Rescue activities The effort and difficulty of a rescue varies widely and depends on many factors such as the nature of the problem, the underwater conditions and the type and depth of the dive site. A simple rescue could be to tow to safety a diver on the surface who is exhausted or suffering from leg cramps. A complex and high-risk rescue would be to locate, free and bring to the surface a lost diver who is trapped underwater in an enclosed space such as a shipwreck or cave with limited breathing gas supplies.
The sequence of potential activities needed in a generic rescue are: Recognising or identifying the need for a rescue if the casualty's position underwater is unknown, locate the casualty and, if possible, mark the position if the casualty is low on breathing gas, provide more gas if the casualty is trapped, free the casualty if the casualty is submerged, bring the casualty to the surface if the casualty has a decompression obligation, decompress if safely possible. The rescuer must also take into account their personal decompression requirements. if the casualty is not buoyant at the surface, make the casualty buoyant if help at the surface is available but not at hand, attract help if the casualty is not breathing, carry out continuous artificial respiration on the surface if the casualty is on the surface in the water and no help is available, tow the casualty to a boat or to land if the casualty is beside a boat or the shore, remove the casualty from the water if necessary, resuscitate, provide first aid and arrange transport to professional medical help
Recognition of an emergency Before any attempt to perform a rescue can be made, a person or group of people who are in a position to initiate appropriate procedures must be aware of the need. This may seem an obvious requirement, but many diving fatalities occur without anyone else knowing that there is a problem, and in many others the problem is initially the loss of information regarding the current status of the diver. This is common in scuba accidents, where separation of the diving team members is often the first indication of a potential problem, and many emergencies are first recognised when a diver fails to surface at the expected time.
Scuba divers generally have no voice communication and are generally restricted to visual signalling. This is limited by line of sight and visibility, which may be poor. In some cases scuba divers may be connected by a tether, or buddy line, which allows communication by line signals, and professional scuba divers often tow a surface marker buoy, which may be used to transmit a very limited range of signals to surface personnel, mainly location of the diver, and if the diver needs help.
Surface supplied divers are less likely to get lost, as they are initially connected to the surface team by at least an airline, and usually also a lifeline which may be used by the line-attendant to communicate with the diver using line signals. Most 21st century surface supplied divers also have voice communication with the surface team, and this allows constant monitoring of the diver's condition by listening to the breathing sounds. Surface supplied divers are therefore able to indicate distress and need for assistance promptly and effectively in almost all cases, and the simple failure to respond appropriately to communications from the surface is also an effective indication of a problem.
Locating the casualty underwater It may be difficult to locate the diver underwater where dives take place in low visibility conditions, in currents or in enclosed spaces such as caves and shipwrecks or where the diver uses breathing equipment which releases few bubbles, such as a rebreather. Even when open circuit equipment is used it may be difficult to see the bubbles due to surface conditions of wind, waves and spray, fog, or darkness.
Surface supplied divers are usually easy to find, as they are at the far end of the umbilical, and it is extremely rare for the umbilical to be completely severed. The standard procedure for rescue of a surface supplied diver is for the standby diver to follow the umbilical to the diver, reporting back frequently to the supervisor on progress.
Divers often use guidelines, surface marker buoys, diving shots, lightsticks and strobe lights to indicate their position to their surface support team. A standard precaution when entering enclosed spaces is to use a guideline to mark the exit route, which may be needed after the diver's fins, wash, and bubbles dislodge silt and loose overhead materials such as rust which can reduce underwater visibility to near zero.
Common search techniques such as the circular search or jackstay search, need preparation and practice if they are to be used effectively and safely. The spiral box search and compass grid search require less preparation, but probably greater skill, and may be rendered ineffective by currents.
Searches of enclosed spaces expose the rescuer to danger. The rescuers may need training and experience in cave diving, ice diving or wreck diving to minimise the risks of that type of rescue.
Providing emergency gas Providing emergency gas to a diver who has run out is the highest priority after finding the diver. Without breathing gas the diver will die in minutes. Running out of gas is a major contributor to diving accidents. Many scuba accidents start in some other way and culminate in running out of gas.
The main reasons for running out of scuba gas are: failing to monitor consumption of the gas - not watching the contents pressure gauge underestimating the amount of gas needed for the return and ascent and decompression stops consuming gas faster than estimated by going too deep, over-exercising or psychological stress delayed exit or ascent due to other problems, such as getting lost or entrapped equipment failure, such as a regulator freeze or blown o-ring, in the breathing apparatus leading to loss of gas.
Even when the prime cause of an underwater emergency is not running out of gas, lack of gas can easily become another problem for the rescuers to overcome because more gas is consumed during the accident and its aftermath. This could be due to the diver remaining at depth for longer than planned or due to increases in the diver's breathing rate, due to exertion, stress or panic.
Common configurations of diving cylinders and diving regulators used as a backup or reserve for emergencies include: An independent set carried by the diver; a complete, backup scuba set such as a bailout cylinder, or the cylinder not currently in use of an independent twin set, or a cylinder not currently in use of a group of side-mounted cylinders, or a separate rescue set brought down by the rescuer, or a "spare air" - a small independent scuba set with integrated regulator and mouthpiece A potentially independent pair of twins connected by an isolation manifold and carried by the diver. If the diver can isolate them in time, the remaining gas in the uncompromised side is available. Sharing gas with another diver via an "octopus regulator" - a second, backup regulator or second stage on a scuba set that is in use by the buddy or rescue diver
There are two main ways of delivering breathing gas to the out-of-air scuba diver; provide the casualty with a separate demand valve, preferably on a long hose or , so that rescuer and casualty can breathe simultaneously, and concentrate their efforts on getting to a safer place, or share a single demand valve with the casualty by "buddy breathing", which is a more risky procedure, and requires constant attention to breathing and management of the demand valve by both divers. The additional task loading of buddy breathing may reduce the capacity of the divers for other activities required for safe resolution of the emergency.
The gas capacity of the cylinder is important. Divers breathing at depth consume more gas because the gas must be delivered to them at ambient pressure, and volumetric breathing gas consumption is driven by partial pressure of arterial carbon dioxide. At the end of a deep dive they will need more gas to breathe during the longer ascent to the surface and during any decompression stops.