existing contingency plan is not normally considered deviation from the plan. In recreational diving, the diver is free to plan or not, and to change the plan on whim, but technical diving certification agencies generally encourage divers to "plan the dive and dive the plan", as this is considered good practice for safety, and is the same strategy used by professionals. Standard operating procedures {SOPs) and codes of practice (CoPs) are used to reduce the amount of detail required in dive planning. These documents provide much of the necessary detail of how frequently encountered tasks should be performed, using methods which have been tested and found to be effective, efficient and acceptably safe. When standard procedures are used, it is not necessary to detail those procedures in the dive plan, as the team members should be familiar with them already. Standard operating procedures are the procedures identified by the diving contractor as the recommended or required way of performing a range of routine activities and codified in a document. Following SOPs is generally a condition of employment for the diving team, and the provision of SOPs may be a requirement of health and safety regulations. The document is often called the operations manual, diving manual or something similar. For example, the U.S. Navy Diving Manual, and NOAA Diving Manual, Codes of practice are procedures identified by a larger population as preferred methods for a similar range of activities. They may be a set of industry best practice recommendations, such as the IMCA Code of Practice for offshore diving, a government regulated set of recommendations, or a regulated set of requirements which must be followed. In recreational diving there are also some procedures that are widely recognised and common to most training agencies, but there are some procedures that differ between agencies, and divers may therefore differ in their expectations in some contingencies. Ideally any two divers intending to dive together in the buddy system, should use the same or compatible responses to emergencies where prompt and effective response could be a matter of life or death. This ideal does not always map well onto the common practice of buddy pairs being allocated more or less arbitrarily by the divemaster or charter boat skipper. The consequence is that some divers accept that the buddy system is degraded by this practice, and they amend their expectations by assuming that the buddy may