Medical screening Fitness to dive, (also medical fitness to dive), is the medical and physical suitability of a diver to function safely in the underwater environment using underwater diving equipment and procedures. Depending on the circumstances it may be established by a signed statement by the diver that he or she does not suffer from any of the listed disqualifying conditions and is able to manage the ordinary physical requirements of diving, to a detailed medical examination by a physician registered as a medical examiner of divers following a procedural checklist, and a legal document of fitness to dive issued by the medical examiner. The most important medical is the one before starting diving, as the diver can be screened to prevent exposure when a dangerous condition exists. The other important medicals are after some significant illness, where medical intervention is needed, and has to be done by a doctor who is competent in diving medicine, and in these cases fitness can not always be established by prescriptive rules. Psychological factors can affect fitness to dive, particularly where they affect response to emergencies, or risk taking behaviour. Overconfidence and trait anxiety are both undesirable characteristics in a diver. The use of medical and recreational drugs, can also influence fitness to dive, both for physiological and behavioural reasons. In some cases prescription drug use may have a net positive effect, when effectively treating an underlying condition, but frequently the side effects of effective medication may have undesirable influences on the fitness of diver, and most cases of recreational drug use result in an impaired fitness to dive, and a significantly increased risk of sub-optimal or inappropriate response to emergencies. Fitness to dive can be modified to some extent by training. Physical fitness can be improved to give the diver better capacity to deal with physical challenges, and properly conducted stress exposure training can improve situational awareness and the ability to focus on relevant responses under stress. Pre-dive preparation and planning Dive planning is the process of planning an underwater diving operation. The purpose of dive planning is to increase the probability that a dive will be completed safely and the goals achieved. Some form of planning is done for most underwater dives, but the complexity and detail considered may vary enormously. Professional diving operations are usually formally planned and the plan documented as a legal record that due diligence has been