Preparation for the dive
The purpose planning for a dive is to ensure that divers do not go beyond their comfort zone or skill level, or the safe capacity of their equipment which includes scuba gas planning to ensure that the amount of breathing gas to be carried is sufficient to allow for any reasonably foreseeable circumstances. Before starting a dive both the diver and their buddy 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. Dive masters may provide useful information and suggestions to assist the divers, but are generally not responsible for the details unless specifically employed to do so.
Standard diving procedures
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 speed; while providing the necessary breathing gas and without losing contact with the other divers in the group.
Equalization 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 equalization 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 are examined to ensure that dissolved gases are safely released, that barotraumas of ascent are avoided, and that it is safe to surface.
Water exit procedures are monitored to leave the water again without injury, loss of, or damage to equipment.
Underwater communication are practiced as 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, and occurs on all scuba divers. 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.
Buddy, team or solo diving Precautions
Buddy and team diving procedures are associated to 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 centered 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. As buddy or team divers are 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 most urgent underwater emergencies usually involve a compromised breathing gas supply. Divers are trained in procedures for donating and receiving breathing gas from each other in an emergency, and may carry an independent alternative air source if they do not choose to rely on a buddy. Divers may need to make an emergency ascent in the event of a loss of breathing gas which cannot be managed at depth.
In the case entrapment the inability to navigate out of an enclosed space can usually be avoided by staying out of enclosed space and when the objective of the dive includes penetration of enclosed spaces, taking precautions such as the use of lights and guidelines, for which specialized training is provided in the standard procedures. While 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 minimize those parts which can easily be snagged, and allow easier disentanglement.
Guide on Depth range Scuba diving
The depth range applicable to scuba diving depends on the application and training. The major worldwide recreational diver certification agencies consider 130 feet (40 m) to be the limit for recreational diving.
Professional scuba diving usually limits the allowed planned decompression depending on the code of practice, operational directives, or statutory restrictions. Depth limits depend on the jurisdiction, and maximum depths allowed range from 30 metres (100 ft) to more than 50 metres (160 ft), depending on the breathing gas used and the availability of a decompression chamber nearby or on site.