A snorkeller was bitten on the buttocks by a shark while out exploring a marine sanctuary, near Exmouth on Christmas Eve.
A WA Fisheries spokesman said the attack, only reported today, happened near Southern Dive Mooring at the Bundegi Sanctuary Zone, PerthNow reports.
He said the victim was snorkelling with her partner 700-1000m from shore in about 5m when a small shark bit her bottom.
The woman did not see the shark and left the water immediately.
She was taken to Exmouth Hospital for treatment.
The species is unknown.