Diver training

The not-for profit agencies tend to focus on developing the diver's competence in relatively fewer stages, and provide more content over a longer programme, than the for-profit agencies, which maximise profit and customer convenience by providing a larger number of shorter courses with less content and fewer skills per course.

Consequently, the entry level certification for most recreational divers advises them to dive only in conditions similar to those in which they were trained, and to a maximum depth of 18 m, with no decompression obligation.

Professional diver training, and the associated assessment and certification of competence, are usually based on occupational health and safety legislation, and also covered by the employer's duty of care.

The most important medical is the one before starting diving, as the diver can be screened to prevent exposure when a dangerous condition exists.

This is typically done by assessment against the requirements of the standards using the same methods as in formal training programmes for safety-critical skills and knowledge, and by accepting verifiable evidence of experience, as in signed and witnessed logbook entries.

Several factors influence the diver, including immersion, exposure to the water, the limitations of breath-hold endurance, variations in ambient pressure, the effects of breathing gases at raised ambient pressure, effects caused by the use of breathing apparatus, and sensory impairment.

Metabolically inactive gases are absorbed by the tissues and may have narcotic or other undesirable effects, and must be released slowly to avoid the formation of bubbles during decompression.

The underwater environment also affects sensory input, which can impact on safety and the ability to function effectively at depth.

In all cases, the symptoms caused by decompression occur during or within a relatively short period of minutes to hours, or occasionally days, after a significant pressure reduction.

[24] Decompression modeling attempts to explain and predict the mechanism of gas elimination and bubble formation within the organism during and after changes in ambient pressure,[27] and provides mathematical models which attempt to predict acceptably low risk and reasonably practicable procedures for decompression in the field.

The field includes the effect of breathing gases and their contaminants under high pressure on the human body and the relationship between the state of physical and psychological health of the diver and safety.

Where risks are marginally acceptable it may be possible to mitigate the consequences by setting contingency and emergency plans in place, so that damage can be minimised where reasonably practicable.

The final product of the planning process may be formally documented or, in the case of recreational divers, an agreement on how the dive will be conducted.

National legislation will commonly be included in the curriculum for entry level professional diving, and may be recognised as prior learning for further diver training.

[41] Divers are instructed and assessed on these skills during basic and advanced training, and are expected to remain competent at their level of certification, either by practice or refresher courses.

Repetition with feedback from the instructor is generally continued until the skill can be performed reliably under normal conditions.

[44] Learning systems that rely on short term cramming and minimum repetition tend to be effective at getting knowledge and skills to a sufficient level that the learner can be pronounced competent against the standard, but this knowledge and skill set is generally lost relatively quickly unless repeated at intervals.

A diver training tank is a container of water large and deep enough to practice diving and underwater work skills, usually with a window through which the exercises can be viewed by the instructor.

A marine scientist or archaeologist may require 3 to 5 years full-time university study to become competent in their chosen field, but can be trained to do the relevant diving in about a month.

Theoretical knowledge and understanding is often amenable to assessment by written examination, which has the advantage of inherently providing a permanent record.

A qualified diver should be a low risk for causing injury or death to themselves or another member of the diving team when operating within the constraints of the training standard.

Periodical competence assessment may be used as a way of keeping track of whether a diver is acceptably up-to-date in a specific skill set.

[53][54] In addition to basic diving skills training, public safety divers require specialized training for recognizing hazards, conducting risk assessments, search procedures, diving in zero visibility, using full-face masks with communication systems, and recovering evidence that is admissible in court.

It is preferable for effective learning and safety that such specialisation training is done systematically and under controlled conditions, rather than on site and on the job.

[58] Members of the IDRF include ADAS (Australia), DCBC (Canada), HSE (UK), PSA (Norway), and the Secretariat General to the Sea Progress Committee (France).

These represent the minimum level of training and competence required to allow scientists to participate freely throughout the countries of the European Union in underwater research projects diving using scuba.

[60] These standards specify the minimum basic training and competence for scientific divers, and do not consider any speciality skill requirements by employers.

[citation needed] British Army and Royal Navy divers are trained at the Defence Diving School at Horsea Island, Plymouth.

[citation needed] In most jurisdictions, no certification is required for freediving, and the equipment is sold freely over the counter with no questions asked of the purchaser's competence to use it.

Most freedivers learn the skills from practice, often with some coaching from a friend, and sometimes attend a formal training programme presented by a qualified and registered instructor, with assessment and certification of competence as the target.