Nautical Twilight focussed on NSW state waters and therefore the interaction of the NSW maritime incident and emergency management arrangements with the National Plan for Maritime Emergencies.

The exercise was held in three phases consisting of a real-time test of the National Maritime Place of Refuge Risk Assessment Guidance (the Guidance), an examination of the wider operational and recovery impacts of a chemical incident in a port and a real time deployment of the National Hazardous and Noxious Substance (HNS) response capability involving deployment of a reconnaissance team to a vessel at sea.