part of diver training is in the emergency procedures known to be effective at managing the most common incidents which could be life-threatening if not managed promptly and appropriately. The amount of overlearning and the level of skill required for certification varies considerably with the training standard for different certifications, but minimum standards for recreational diver and instructors have been established by the International Standards Organisation (ISO), and national and international standards for professional divers have been published by various controlling bodies. All of these standards include management of the most frequent diving emergencies by application of well established techniques, though not always by identical procedures. Emergency and rescue: procedures, personnel and equipment The diver should be able to manage a reasonably foreseeable and immediately life-threatening emergency unaided as there can be no guarantee that someone else will be near enough to help, will notice and will respond appropriately in time. Lower priority threats can be managed by teamwork and resource sharing. Since most of the critical safety skills for diving are not intuitive, nor associated with activities the diver is likely to have learned for other purposes, diver safety is enhanced by comprehensive training and frequent exercise of safety critical skills. One of the standard ways to help the diver to manage an emergency is to provide another diver ready to assist. In professional diving this is known as the stand-by diver, and in the case of bell diving, the bellman. In technical diving, similar roles may be filled by support divers. In recreational diving, buddy diving and team diving procedures are intended to provide similar benefits, where each diver in a pair or team is stand-by diver to the other or others. This system can be effective when the divers are all adequately skilled, fit and dedicated to the task, as has been shown in many deep dives and cave penetrations. The buddy diver is less effective when insufficiently skilled, inattentive, or unfit. Buddy and team diving procedures impose a significant additional task loading on the divers, particularly in adverse conditions, such as darkness, low visibility, confined spaces, strong currents, cold water and unfamiliarity with each other's equipment and habits. Nevertheless, many recreational training agencies maintain that buddy diving is intrinsically safer than solo diving. Stand-by diver The stand-by diver's job is to wait until something goes wrong, and then be sent in to sort it out. For