Simulated disease outbreaks are vital tools for preparing administrative and functional responses to emergencies. Three aquatic emergency response exercises conducted in Australia are summarised. The prinicipal lesson learned from these exercises was the need for coordination, improved communication and a whole-of-government approach. An enhanced understanding of the legislative instruments required for a response, insights into human factors such as staff rostering, training, counselling and provision of assistance packages were also obtained. Developing a sense of overconfidence about preparedness arrangements (as a result of having tested specific, planned scenarios) must be avoided. Emergencies occur infrequently and erratically; conducting exercises is a vital component of planning processes that ensure that responses to emergency events are effective.