goes wrong, and the diver's residual capacity is not enough to cope with the changed circumstances. This can be followed by a cascade of failures, as each problem loads the diver more and triggers the next. In such cases the diver is lucky to survive, even with the assistance of a buddy or team, and there is a significant risk of others becoming part of the accident. Diving team performance A dive team can vary from a recreational buddy pair to a professional saturation diving team working 24 hours per day with dive and habitat support personnel on a dynamically positioned vessel. The primary purpose of a professional diving team is to improve safety for the working diver by providing backup and support, and to manage the surface equipment required for the operation. A buddy pair is a team intended to improve the safety of recreational divers, and in some circumstances succeeds in this aim, depending on the skills, situational awareness and compliance with procedures of both of the divers. Technical diving teams can vary between the recreational buddy pair at its worst to expedition teams with structure, competence and planning similar to professional teams. For buddy diving to be an effective means of improving safety, the buddy pairs should be set long enough before the dive to allow adequate familiarisation with each other's equipment, signals and procedures, where they differ, and discuss the dive plan, and kit-up should occur in close enough proximity for both divers to actually monitor the progress and details of pre-dive checks, and where necessary, to assist directly with fitting equipment. For many applications, the minimum personnel requirement for a professional diving operation is a working diver, to do the job, a diver's tender to assist the diver and manage the umbilical or airline, a stand-by diver, competent and ready to go to the assistance of the working diver, and a supervisor, to co-ordinate the team, ensure that the plan is acceptably safe in terms of the organisational policies coded of practice and applicable legislation, ensure that the operation follows the plan as far as possible, and to manage any contingencies or emergencies that may come up during the operation. The primary responsibility of the supervisor of a professional diving team is the health and safety of the diving team. The minimum personnel requirement for a recreational dive in most places, is the diver. There