To give the discussion a bit more perspective, the following is a summary of the total number of fatal shark attacks in Western Australia taken from the Shark Attack Files SAS.
Shark Attack File SAS World Wide international global Shark Attack File Year..........Number......Fatalities...Shark ................Attacks 1800-1809.... 1............ NR......... NR 1810-1819.... NR.......... NR..........NR 1820-1829.... NR.......... NR..........NR 1830-1839.... NR.......... NR..........NR 1840-1849.... NR.......... NR..........NR 1850-1859.... NR.......... NR..........NR 1860-1869.... NR.......... NR..........NR 1870-1879.... 2............ 1............ NR 1880-1889.... 1............ NR.......... NR 1890-1899.... 3............ 2............ NR,NR 1900-1909.... 3............ 1............ NR 1910-1919.... 5............ 1............ NR 1920-1929.... 8............ 4............ NR,NR,NR,T 1930-1939.... 3.............NR.......... NR 1940-1949.... 7............ 2............ T,T 1950-1959.... 9............ 1............ T 1960-1969.... 26.......... 1............ W 1970-1979.... 5............ NR.......... NR 1980-1989.... 9............ NR.......... NR 1990-1999.... 11.......... 2............. T,W 2000-2009.... 30.......... 4............. W,W,W,W 2010-2014.... 24.......... 8............. NR,NR, W,W,W,W,W,W Codes: NR - None recorded T - Tiger shark W - White pointer Number of attacks includes fatalities. Note that there has been a dramatic increase in the number of fatal shark attacks since 1997 when the white pointer was first protected in this state and most of these attacks were by white pointers. Also note that we're not yet halfway through the latest 2010-2019 interval. Should the number of fatal attacks continue at the current rate we can expect at least another eight fatal attacks by the end of 2019 bringing the total to 16 for this interval. My quick scan of the Shark File data suggests the rate of fatal attacks in our area (within 300 km of Perth as defined in the OP) is among the highest anywhere in the world. We had five fatal attacks in the space of twelve months in the past few years. It is likely this disturbing trend will continue without intervention. The question posed in the OP was, suppose this occurred in the region where you dive and the number of fatalities continued to escalate at this rate. At what point would you stop diving? How much risk would you tolerate? This is a question being asked by many divers in my area. It is a question that should be considered by tourists who travel to locations such as ours and dive.