This appears to have been more cyclone than tornado.
My understanding of cyclones is that they form and are energised in warm tropical waters and they fizzle out over land or when they reach cool water. Have you ever swum in sea water in SA?
News reports say tornados took out the power towers. Before you become too skeptical it might be wise to check whether the claims are exaggerated.
A 'tornado' filmed in South Australia - ABC News (Australian Broadcasting Corporation)