The shark interaction occurred near Town Beach in Mandurah about 7.14am (10.14am ESDT), which led to the beach being closed and a public warning was issued while experts assessed the situation.
The jetski rider was uninjured after the close encounter.
“Adhere to beach closures advised by Local Government Rangers, Parks and Wildlife Service officers or Surf Life Saving WA,” the alert said.
It comes just a day after Australia was named the top country in the world for fatal shark attacks.
Of the 10 fatal shark attacks in the world last year, four happened in Australian waters.
