For the diver who is adequately trained and physically fit, who is aware of the limitations of the equipment and who appreciates the specific requirements of different environmental diving conditions, the sea is rarely dangerous. Nevertheless, it can be hazardous and unforgiving if attention is not paid to all these factors.
Diver training is specific to the environment in which the diver is trained. Specialized techniques are recommended to cope with different environments. They cannot be automatically extrapolated to other diving environments. The induction of fear in the inexperienced diver and of physical stress in the more skilled diver is appreciated only when one examines each specific environmental threat. These environmental stresses are mentioned in this and other chapters. The reason for including them in a medical text is that unless the physician comprehends the problems and dangers, the medical examinations for diving fitness and the assessments of diving accidents will be less than adequate.
Some aspects of the environments have physiological and pathological sequelae and therefore have specific chapters devoted to them. They include the effects of cold (see Chapters 27 and 28), altitude and fresh water diving (see Chapter 2), explosives (see Chapter 34), depth (see Chapters 2, 15, 20, 46 and 68) and marine animal injuries (see Chapters 31 and 32). Other environmental topics that are covered more comprehensively in diving texts are summarized in this chapter.
Being kept underwater and exceeding the limited air supply will result in drowning. This is a situation common to many of the hazardous environments, including caves and wrecks and under ice, overhangs, water flows and so forth. A variety of materials can trap the diver, including kelp, lines (even ‘safety’ lines), fishing nets and fishing lines. If the diver does not have a compromised air supply, then knowledge of the environment, a buddy, a communication facility, a calm state of mind and a diving knife or scissors will cope with most of these circumstances.