sentences:  "Attack" class patrol boat HMAS "Ambush" (portrayed by HMA Ships and ) was used in the first season, with filming taking place during 1978 and 1979 around Sydney Harbour, Pittwater, Ku-ring-gai Chase, and the Hawkesbury River.For the second season, the crew transferred to the newer "Fremantle" class patrol boat HMAS "Defiance" (portrayed by HMA Ships , , , , and ).The series is similar to the BBC series "Warship", screened by the Australian Broadcasting Corporation from 1976, before "Patrol Boat".