The underwater environment is unfamiliar and hazardous, and to ensure diver safety, simple, yet necessary procedures must be followed. A certain minimum level of attention to detail and acceptance of responsibility for one’s own safety and survival are required. Most of the procedures are simple and straightforward, and become second nature to the experienced diver, but must be learned, and take some practice to become automatic and faultless, just like the ability to walk or talk. Most of the safety procedures are intended to reduce the risk of drowning, and many of the rest are to reduce the risk of barotrauma and decompression sickness. In some applications getting lost is a serious hazard, and specific procedures to minimise the risk are followed.
The skills include selection, functional testing, preparation and transport of scuba equipment, dive planning, preparation for a dive, kitting up for the dive, water entry, descent, breathing underwater, monitoring the dive profile (depth, time and decompression status), personal breathing gas management, situational awareness, communicating with the dive team, buoyancy and trim control, mobility in the water, ascent, emergency and rescue procedures, exit from the water, unkitting after the dive, cleaning and preparation of equipment for storage and recording the dive, within the scope of the diver’s certification.
Preparation for the dive
The purpose of dive planning is to ensure that divers do not exceed their comfort zone or skill level, or the safe capacity of their equipment, and includes scuba gas planning to ensure that the amount of breathing gas to be carried is sufficient to allow for any reasonably foreseeable contingencies. Before starting a dive both the diver and their buddy[note 2] do equipment checks to ensure everything is in good working order and available. Recreational divers are responsible for planning their own dives, unless in training, when the instructor is responsible. Divemasters may provide useful information and suggestions to assist the divers, but are generally not responsible for the details unless specifically employed to do so. In professional diving teams all team members are usually expected to contribute to planning and to check the equipment they will use, but the overall responsibility for the safety of the team lies with the supervisor as the appointed on-site representative of the employer.
Standard diving procedures
Some procedures are common to almost all scuba dives, or are used to manage very common contingencies. These are learned at entry level and may be highly standardised to allow efficient cooperation between divers trained at different schools.
Water entry and descent procedures are carried out first to enter the water without injury or loss of/damage to equipment. These procedures also cover how to descend at the right place, time, and rate; with the correct breathing gas available; and without losing contact with the other divers in the group.
Equalisation of pressure in gas spaces to avoid barotraumas. The expansion or compression of enclosed air spaces may cause discomfort or injury while diving. Critically, the lungs are susceptible to over-expansion and subsequent collapse if a diver holds their breath while ascending: during training divers are taught to never hold their breath while diving. Ear clearing is another critical equalisation procedure, usually requiring conscious intervention by the diver.
Mask and regulator clearing may be needed to ensure the ability to see and breathe in case of flooding. This can easily happen and is not considered an emergency.
Buoyancy control and diver trim require frequent adjustment (particularly during depth changes) to ensure safe and convenient underwater mobility during the dive.
Buddy checks, breathing gas monitoring, and decompression status monitoring are carried out to ensure that the dive plan is followed and that members of the group are safe and available to help each other in an emergency.
Ascent, decompression, and surfacing: to ensure that dissolved gases are safely released, that barotraumas of ascent are avoided, and that it is safe to surface.
Water exit procedures: to leave the water again without injury, loss of, or damage to equipment.
Underwater communication: Divers cannot talk underwater unless they are wearing a full-face mask and electronic communications equipment, but they can communicate basic and emergency information using hand signals, light signals, and rope signals, and more complex messages can be written on waterproof slates.
Inert gas components of the diver’s breathing gas accumulate in the tissues during exposure to elevated pressure during a dive, and must be eliminated during the ascent to avoid the formation of symptomatic bubbles in tissues where the concentration is too high for the gas to remain in solution. This process is called decompression. Most recreational and professional scuba divers avoid obligatory decompression stops by following a dive profile which only requires a limited rate of ascent for decompression, but will commonly also do an optional short shallow decompression stop known as a safety stop to further reduce risk before surfacing. In some cases, particularly in technical diving, more complex decompression procedures are necessary. Decompression may follow a pre-planned series of ascents interrupted by stops, or may be monitored by a personal decompression computer.
These include debriefing where appropriate, and equipment maintenance, to ensure that the equipment is kept in good condition for later use.
Buddy, team or solo diving
Buddy and team diving procedures are intended to ensure that a recreational scuba diver who gets into difficulty underwater is in the presence of a similarly equipped person who understands and can render assistance. Divers are trained to assist in those emergencies specified in the training standards for their certification, and are required to demonstrate competence in a set of prescribed buddy assist skills. The fundamentals of buddy/team safety are centred on diver communication, redundancy of gear and breathing gas by sharing with the buddy, and the added situational perspective of another diver.
Solo divers take responsibility for their own safety and compensate for the absence of a buddy with skill, vigilance and appropriate equipment. Like buddy or team divers, properly equipped solo divers rely on the redundancy of critical articles of dive gear which may include at least two independent supplies of breathing gas and ensuring that there is always enough available to safely terminate the dive if any one supply fails. The difference between the two practices is that this redundancy is carried and managed by the solo diver instead of a buddy. Agencies that certify for solo diving require candidates to have a high level of dive experience – usually about 100 dives or more.
Since the inception of scuba, there has been ongoing debate regarding the wisdom of solo diving with strong opinions on both sides of the issue. This debate is complicated by the fact that the line which separates a solo diver from a buddy/team diver is not always clear. For example, should a scuba instructor (who supports the buddy system) be considered a solo diver if their students do not have the knowledge or experience to assist the instructor through an unforeseen scuba emergency? Should the buddy of an underwater photographer consider themselves as effectively diving alone since their buddy (the photographer) is giving most or all of their attention to the subject of the photograph? This debate has motivated some prominent scuba agencies such as Global Underwater Explorers (GUE) to stress that its members only dive in teams and “remain aware of team member location and safety at all time.” Other agencies such as Scuba Diving International (SDI) and Professional Association of Diving Instructors (PADI) have taken the position that divers might find themselves alone (by choice or by accident) and have created certification courses such as the “SDI Solo Diver Course” and the “PADI Self-Reliant Diver Course” in order to train divers to handle such possibilities.
The diver has a very limited ability to survive without a supply of breathing gas. Any interruption to that supply must be considered a life-threatening emergency, and the diver should be prepared to deal effectively with any reasonably foreseeable loss of breathing gas. Temporary interruptions due to flooding or dislodging the demand valve are recoverable by recovery and clearing of the demand valve. More permanent interruptions require other strategies. An obvious response which is appropriate in some circumstances is to ascend to the surface. This response is appropriate when the consequences are acceptable. When the surface is near enough to easily be reached, and the diver has no significant risk of decompression sickness as a consequence of a direct ascent, an emergency free ascent may be a suitable response. If the surface is too far to reach with confidence, or if the risk of decompression sickness is unacceptable, other responses would be preferable. These involve getting an alternative supply of breathing gas, either from an alternative source carried by the diver, or from another diver.
An emergency ascent usually refers to any of several procedures for getting to the surface in the event of an out-of-air emergency, generally while scuba diving.
Emergency ascents may be broadly categorized as independent ascents, where the diver is alone and manages the ascent alone, and dependent ascents, where the diver is assisted by another diver, who generally provides breathing gas, but may also provide transportation or other assistance. Emergency ascent usually refers to cases where the distressed diver is at least partially able to contribute to the management of the ascent.
An emergency ascent implies that the diver initiated the ascent intentionally, and made the choice of the procedure. Ascents that are involuntary or get out of control unintentionally are more accurately classed as accidents.
Emergency ascents may be classified as independent action, where no assistance required from another diver, and dependent action, where assistance is provided by another diver.
Buoyant ascent is an ascent where the diver is propelled towards the surface by positive buoyancy.
Controlled emergency swimming ascent (CESA) is an emergency swimming ascent which remains under control and which is performed at a safe ascent rate, with continuous exhalation at a rate unlikely to cause injury to the diver by lung over-expansion.
Emergency swimming ascent (ESA) is a free ascent where the diver propels him/herself to the surface by swimming at either negative or approximately neutral buoyancy.
Another form of ascent which may be considered an emergency ascent is a tethered-ascent – where the diver has unintentionally lost full control of buoyancy due to a loss of ballast weight, and controls ascent rate by use of a ratchet dive reel with the end of the reel line secured to the bottom.
Emergency ascent training policy differs considerably among the certification agencies, and has been the subject of some controversy regarding risk-benefit.
Emergency air sharing
Emergency sharing of breathing gas may be done by sharing a single demand valve, or by the donor providing a demand valve to the receiver, and another for their own use. The gas supply for the second demand valve may be from the same scuba set or from a separate cylinder. The preferred technique of air sharing is donation of a demand valve that is not needed by the donor.
The procedure of sharing a demand valve is known as buddy breathing. It is no longer considered the default method of sharing breathing gas as the use of a separate “octopus” demand valve is considered to reduce the risks involved sufficiently to justify it being rated the standard practice by most, if not all, diving certification agencies. As a consequence, buddy breathing is no longer taught as extensively as it was in the past, but some agencies and schools still teach buddy breathing as an entry-level or advanced skill, as the ability to perform the skill successfully is not only considered a potentially life-saving skill in special circumstances, but also demonstrates the self-control and rational behavior that are desirable in an emergency. The standard technique for buddy breathing is for the divers to alternately breathe from the demand valve, usually each taking two breaths before exchanging the DV, but it is common for the receiver to be out of breath at the start of the procedure, and they may need a few more breaths to stabilize. Once a rhythm has been established, it is usual to terminate the dive and start the ascent, so buddy breathing training will usually include assisted ascents. Assisted ascents using a secondary demand valve are simpler than buddy breathing ascents, and this skill is quicker to learn.
The conventional technique, known as octopus donation, is to donate a secondary demand valve supplied from the donor’s primary gas supply, known as an octopus DV, which is mounted ready for use in an easily accessible position in the donor’s chest area, and is often yellow for easy recognition.
The alternative is to donate the primary demand valve that the donor is currently breathing from, on the principle that it is known to be working and is immediately recognizable and accessible. The donor, who should be less stressed, will then switch to the secondary demand valve, which in this arrangement is generally mounted on a loop of bungee cord which hangs on the neck, and keeps the secondary demand valve tucked up under the diver’s chin, where it can often be reached without the use of the hands, by bending the head forward and gripping the mouthpiece with the teeth.
Bailout to alternative gas supply
An alternative to relying on a dive buddy to supply breathing gas in an emergency, is to carry an independent supply of emergency breathing gas in a separate cylinder, known variously as an independent alternative air source, bailout cylinder or pony cylinder. This is necessarily the option used by solo divers, as they may not be anywhere near another diver in an emergency, but it is also the choice of many professional diving organisations and conventional recreational divers, who prefer not to rely on an unfamiliar buddy. The details of the technique vary depending on how the bailout cylinder is carried. This skill is generally not taught to entry level recreational divers, but may be part of the basic required skill set for professional divers.
Standardised emergency procedures used with manifolded twins
One of the standardised configurations used with manifolded twins is that developed by the DIR movement for cave exploration. The procedures listed are those developed for this configuration, and are in general use by a large number of technical divers. The diver breathes from the primary second-stage regulator supplied from the right side first stage by a long (2-meter/7-foot) hose. A secondary second-stage regulator is carried just beneath the chin, suspended by a breakaway elastic loop around the neck, supplied from the left side first stage cylinder by a shorter (0.5-meter/2-foot) hose. The cylinder valves and manifold isolation valve are normally open:
If another diver experiences an out-of-air emergency, the donor diver hands over the primary regulator, which they both know is functioning properly. The donor then switches to the secondary regulator. The entire gas supply is available to both divers for the remainder of the dive and they are able to separate by a sufficient distance to pass through tight restrictions with the donor behind the recipient.
If the primary regulator malfunctions, the diver closes the right-shoulder cylinder valve and switches to the secondary regulator. The entire gas supply is available for the remainder of the dive.
If the secondary regulator malfunctions, the diver closes the left-shoulder cylinder valve, continuing to breathe through the primary regulator. The entire gas supply is available for the remainder of the dive.
Cylinder to manifold connection malfunction, though rare, can result in an extremely violent gas loss. In case of the right side manifold connection leak, the diver closes the isolating valve to secure the gas in the left cylinder, and continues to use the gas from the right cylinder until it runs out, and then switches to the secondary regulator. At least half of the remaining gas volume is available for the remainder of the dive once the isolation valve has been closed.
In case of the left side manifold connection leak, the diver closes the isolating valve switches to the secondary regulator to use as much of the gas in the left cylinder as practicable before it runs out, then switches back to the primary regulator. At least half of the remaining gas volume is available for the remainder of the dive once the isolation valve has been closed.
Dive management skills
Monitoring depth and time
Whenever there is a possibility that the pressure exposure of a dive may incur a decompression obligation on the diver it is necessary for safety to monitor the depth and duration of the dive to ensure that either there is no decompression obligation, or that the appropriate decompression procedures are followed for a safe ascent. This process may be automated by using a personal dive computer, in which case the diver is required to understand how to read the output and follow the decompression instructions displayed. The display and operation of dive computers is not standardized, and the user is expected to learn the correct operation of the specific model of computer to be used before diving with it. Accurate monitoring of depth and time is particularly important when diving using a schedule requiring decompression according to decompression tables.
Breathing gas management
Management of breathing gas is a critical skill for scuba diving, as the scuba diver must, by definition, carry all the required breathing gas for a dive, and running out unexpectedly is at best alarming, and at worst can have fatal consequences. For the basic case of no-decompression open-water diving, where a free ascent is acceptable in an emergency, this may be as simple as ensuring that sufficient air remains in the cylinder to allow a safe ascent at any time, usually allowing for a contingency reserve, and for the possibility of an assisted ascent, where the diver supplies breathing gas to a buddy. Gas management becomes more complex when solo diving, decompression diving, penetration diving, or diving with more than one gas mixture.
A submersible pressure gauge is used to indicate the remaining gas pressure in a diving cylinder. The amount of available gas remaining can be calculated from the pressure and the cylinder internal volume, and the time that he diver can dive on the available gas depends on the depth and work load, and the fitness of the diver. Breathing rates can vary considerably, and estimates are largely derived from experience. Conservative estimates are generally used for planning purposes.
Use of auxiliary equipment
These are generally considered advanced techniques by recreational certification agencies, but may be considered basic skills for professional divers.
Bailout to a redundant gas supply: Switching to a bailout cylinder in case of main gas supply failure. The techniques vary depending on how the cylinder is carried and what type of mask is used.
Use of surface marker buoys: A surface marker buoy is useful to indicate the position of the diver to people on the surface. Control of line tension is important to prevent entanglement and snagging.
Use of decompression buoys: Sub-surface deployable buoys allow the diver to signal that the ascent has begun, and indicate the position of the diver to people on the surface, often the crew of the boat which must pick the divers up after the dive. Deployment skills include controlled inflation, paying out line in a way they avoids snags and jams, maintaining appropriate depth control during the deployment and control of line tension during ascent.
Use of distance lines
Use of shot lines: Shotlines are used to indicate a position so that divers can reach the bottom at the right place, and ascend to the surface where the surface crew expects them. The choice, rigging and deployment of shotlines to suit the dive profile and environmental conditions is also a diving skill.
Underwater navigation, using Compass and underwater pilotage
In-water decompression stops: Divers who may develop a decompression obligation need to be able to follow the required decompression profile to avoid decompression sickness. This requires the ability to maintain fairly accurate depth for the required periods, and to ascend at the correct rate. Some divers have the skills to do this independently of a static reference, referring only to depth and time instrument displays, others rely on a decompression buoy or shotline to monitor and help control changes of depth.
Analyzing nitrox mixtures for oxygen fraction: The safe use of nitrox mixtures depends on using them at depths where the partial pressure of oxygen is within acceptable limits, and this requires knowledge of the oxygen fraction, so the maximum operating depth can be calculated. Recreational divers are responsible for analysis of their own breathing gas.
Switching gases for accelerated decompression: A critical skill for this procedure is positive identification of the breathing gas in use at any time, as decompression mixtures are generally extremely dangerous to breathe at the maximum depth of the dive
Use of lifelines and buddy lines.
Diver rescue skills
Diver rescue, following an accident, is the process of avoiding or limiting further exposure to diving hazards and bringing a diver to a place of safety 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. Rescue skills are considered by some agencies to be beyond the scope of entry level divers, but other agencies consider some or all of them an essential part of the entry level diving skill set, as this is more compliant with the concept of buddy diving, and a required part of the skill set for a stand-by diver.
Diver rescue skills include:
Controlled buoyant lift – a technique used to safely raise an incapacitated diver to the surface from depth. It is the primary technique for rescuing an unconscious diver. It can also be used where the casualty has lost or damaged his or her diving mask and cannot safely ascend without help.
Making the casualty buoyant on the surface.
Towing a diver on the surface
Landing a casualty.
In-water artificial respiration
CPR on land or a boat
Oxygen first aid on land or a boat
General First aid
More than one technique may be taught for any of these skills, the choice depending on the standards of the training agency.
Basic rebreather diving skills
Preparing the Rebreather: The rebreather may require some assembly before use, and should be tested for correct function according to the manufacturer’s recommendations. The scrubber canister must be filled with the correct amount of absorbent material, and the unit tested for leaks. Two leak tests are usually conducted. These are generally known as the positive and negative pressure tests, and test that the breathing loop is airtight for internal pressure lower and higher than the outside. The positive pressure test ensures that the unit will not lose gas while in use, and the negative pressure test ensures that water will not leak into the breathing loop where it can degrade the scrubber medium or the oxygen sensors.
Prebreathing the unit (usually for about 3 minutes) shortly before entering the water is a standard procedure. This ensures that the scrubber material gets a chance to warm up to operating temperature, and works correctly, and that the partial pressure of oxygen in a closed-circuit rebreather is controlled correctly.
Buoyancy control using the Rebreather
Ascents and descents
Monitoring the partial pressure of oxygen: Partial pressure of oxygen is of critical importance on CCR’s and is monitored at frequent intervals, particularly at the start of the dive, during descent, and during ascent, where the risk of hypoxia is highest.
Monitoring carbon dioxide level: Carbon dioxide buildup is also a severe hazard, and most rebreathers do not have electronic CO2 monitoring. The diver must look out for indications of this problem at all times.
Diving mask clearing and dive/surface valve draining
Bailing out to an alternative breathing gas supply: Bailout to open circuit is generally considered a good option when there is any uncertainty as to what the problem is or whether it can be solved. The procedure for bailout depends on details of the rebreather construction and the bailout equipment chosen by the diver. Several methods may be possible:
Bailout to open circuit by switching the mouthpiece bailout valve to open circuit.
Bailout to open circuit by opening a bailout demand valve already connected to the full face mask, or by nose-breathing in some cases.
Bailout to open circuit by closing and exchanging the rebreather mouthpiece for a separate demand valve.
Bailout to rebreather by closing the mouthpiece and switching to the mouthpiece of an independent rebreather set.
Bail out ascent: Unless the problem can be corrected fairly quickly and reliably, bailout will include aborting the dive and ascent.
Diluent flush: Many diver training organizations teach the “diluent flush” technique as a safe way to restore the mix in the loop to a level of oxygen that is neither too high nor too low. It only works when partial pressure of oxygen in the diluent alone would not cause hypoxia or hyperoxia, such as when using a normoxic diluent and observing the diluent’s maximum operating depth. The technique involves simultaneously venting the loop and injecting diluent. This flushes out the old mix and replaces it with a known proportion of oxygen.
Draining the loop: Regardless of whether the particular rebreather has the facility to trap any ingress of water, training on a rebreather will feature procedures for removing excess water from the loop.
Scuba skills for special applications
There are a range of special applications for scuba diving for which additional skill sets are required. In many cases the skills for one of these special applications may be shared by several others, with a few specific only to that application. There are also many underwater work and activity skills not directly related to the use of scuba equipment.
Some of these applications are listed here:
Side mount diving
Underwater search and recovery
Training, assessment and certification
Scuba skills training is primarily provided by practical instruction under the guidance of a registered or certified diving instructor, on the assumption that the instructor is both competent and willing to provide a quality of training and assessment according to the relevant training standards, and to ensure that the learner is competent according to the assessment criteria applied. Additional practice of the skills is the responsibility of the diver, and is generally necessary to reach and retain a level of competence sufficient to deal with the foreseeable contingencies which may occur during diving under the range of conditions in which the diver is certified to dive. Recreational divers may attend refresher courses when they have not dived for a significant period, in which the instructor ensures that they are still competent in the skills required by their certification, and it is not uncommon for service providers like dive shops and charter boats to require a checkout dive from divers unfamiliar with the region, or unable to show sufficient evidence of adequate current skill level. The checkout dive is usually a demonstration by the diver of basic skills appropriate to the expected conditions, and may be assessed by an instructor or divemaster. These refresher courses and checkout dives are usually informal, and may vary considerably.
It is the individual diver’s responsibility to maintain sufficient skill and fitness to dive safely and not endanger themself or other divers, and to judge whether they are competent and fit to dive in any given circumstance, based on the information available and a realistic dive briefing by the service provider.
Recreational diver training
Many recreational diver training organizations exist, throughout the world, offering diver training leading to certification: the issuing of a “Diving Certification Card,” also known as a “C-card,” or qualification card.
Recreational diver training courses range from minor specialties which require one classroom session and an open water dive, and which may be completed in a day, to complex specialties which may take several days to weeks, and require several classroom sessions, confined water skills training and practice, and a substantial number of open-water dives, followed by rigorous assessment of knowledge and skills. Details on the approximate duration of training can be found on the websites of most certification agencies, but accurate schedules are generally only available from the specific school or instructor who will present that course, as this will depend on the local conditions and other constraints.
The initial open water training for a person who is medically fit to dive and a reasonably competent swimmer is relatively short. Many dive shops in popular holiday locations offer courses intended to teach a novice to dive in a few days, which can be combined with diving on the vacation. Other instructors and dive schools will provide more thorough training, which generally takes longer.
Diving instructors affiliated to a diving certification agency may work independently or through a university, a dive club, a dive school or a dive shop. They will offer courses that meet, or exceed, the standards of the certification organization that will certify the divers attending the course.
Technical diver training
Technical diver training generally follows a similar pattern to other recreational diver training, but tends to provide a more comprehensive level of theoretical learning, and in many cases, a far more exhaustive level of skill over-training, with higher standards for assessment, as the risks are higher and the necessary competence to manage reasonably foreseeable contingencies is more complex.
Professional diver training
Professional diver training is generally provided by schools affiliated to or approved by one or more of the commercial, scientific or other professional diver certification or registration organizations. Professional diver training standards may require a significantly higher level of over-training than most recreational certification agencies, as the professional diver is expected to manage most contingencies and still perform the planned work under difficult conditions. Professional divers may also be provided with what is variously known as confidence training or stress training, where simulated emergencies are enacted, or unlikely contingencies are simulated, with the intended result of developing the diver’s confidence in their ability to manage contingencies while in a controlled environment. The amount of time spent on skill and confidence development is generally proportional to the length of the training programme, as the basic skills are usually learned fairly quickly.
Source from Wikipedia