Police said the 17-year-old was in the water with her father near the town of Esperance when she was attacked on Monday afternoon.
Tragically, the teen, who lost a substantial amount of blood, later died from the injuries sustained.
This is a developing story.
The teenager was believed to have lost one of her legs in the attack, Seven News reported. She was treated by paramedics before being taken to the hospital, where she later died.
Police have not said what type of shark was responsible but are being helped in their investigation by the department of fisheries.
Authorities closed Wylie Bay Beach until further notice.
The coastline is known for sightings of great white sharks.
Her mother and two sisters reportedly watched in horror from the beach as the she was attacked by the shark. It was reported that two great white sharks were involved in that incident.