The aircraft had been tasked by police to provide assistance to two people in difficulty in Lake Munmorah. With the aircraft in the hover, the crewman stepped into the water with the intention of assisting the swimmers. As the water was shallow, the crewman's foot hit the bottom of the lake hard, breaking his ankle. People from the shore rescued the swimmers and the crewman in the water. The crewman was later flown to hospital for medical treatment. The crew's actions were in accordance with their training and the company's operations manual. However, these procedures contain a latent failure in that they are not safe in shallow water or where there may be submerged objects. Since this occurrence, procedures have been changed so that crewman can only jump from the aircraft when it is out to sea. A crewman who needs to enter the water in a bay, lake or river has to be winched into the water. The operations manual has been amended to avoid a repeat of this occurrence. No further safety action is required.