There is some confusion, and consequent variation in policy, between the agencies responsible for the search, rescue and resuscitation of submersion victims regarding the likelihood of survival following a period of submersion. The aim of this work was to recommend a decision-making guide for such victims. This guidance was arrived at by a review of the relevant literature and specific case studies, and a “consensus” meeting on the topic. The factors found to be important for determining the possibility of prolonged survival underwater were: water temperature; salinity of water; duration of submersion; and age of the victim. Of these, only water temperature and duration are sufficiently clear to form the basis of guidance in this area. It is concluded that if water temperature is warmer than 6°C, survival/resuscitation is extremely unlikely if submerged longer than 30 min. If water temperature is 6°C or below, survival/resuscitation is extremely unlikely if submerged longer than 90 min.