Australians who have won 8 olympic medals in swimming?

Petria Thomas

Games: 1996, 2000, 2004

3 Gold, 4 Silver, 1 Bronze

Dawn Fraser

Games: 1956, 1960, 1964

4 Gold, 4 Silver

And the third? Well, there isn't one!

The next Australian swimmer on the list is Shirley Strickland; at the 1948, 1952, and 1956 Olympics, she won 7 medals: 3 Gold, 1 Silver, 3 Bronze.

Source:

http://en.wikipedia.org/wiki/List_of_multiple_Olympic_gold_medalists