This study deals with the creation of an assessment basis for the water-side safeguarding of events. It is meant to give acting persons, authorities and organisations a calculation basis for the safeguarding of events in, on and next to water. To do this, risk factors are initially identified and assessed. In the next step an accident probability is calculated based on empirical data from the lifeguard services. Next, the number of expected emergencies for an event is determined with the identified probability and the risk value. Then a plan for space and manpower for an event is carried out with the lifeguard service planning methods. Finally, the user receives the required number of operating workforces and resources for the comprehensive safeguarding of the event. The results of the study is a calculation algorithm, which can be used to determine the necessary safeguarding measures. A risk-adequate safeguarding of an event in, on or next to water is therefore possible.