This unit describes the performance outcomes, skills and knowledge required to act as a standby diver in support of diving operations (from a platform and in-water) in an open water environment.It includes preparing and positioning required diving equipment and emergency resources; meeting the readiness states as detailed by the dive supervisor; maintaining communications with dive supervisor throughout the dive; and taking rapid steps to resolve incidents, ranging from resupplying emergency breathing gas reserves to locating and rescuing injured or unconscious diver/s.This unit relates, in part, to existing standards in the Australian Diver Accreditation Scheme (ADAS).This unit was developed for Defence divers but may be applicable to anyone in this field.The skills and knowledge described in this unit must be applied within the legislative, regulatory and policy environment in which they are carried out. Organisational policies, dive plan and procedures must be consulted and adhered to.Persons undertaking this unit work independently and perform specific tasks in a range of contexts that could be unpredictable.No licensing, legislative or certification requirements apply to this unit at the time of publication.