The Department of Fisheries will be keeping an eye on beaches across Mandurah today after an untagged shark was reported in the area late yesterday.
Gearys Beach was closed when an untagged shark knocked a surfer from his board yesterday evening.
The swimmer described the impact as "a very solid bump."
It was reported around 4.50pm yesterday and lead authorities to close the beach.
Shark Warning signs have been erected by City of Mandurah rangers with Fisheries officers patrolling all beaches in the area across the day.
The Westpac Surf Life Saving Rescue Helicopter will also conduct areal patrols.
Swimmers are advised to adhere to beach closures, take caution in the water and check the SharkSmart website or Surf Life Saving WA Twitter Feed for updates.
If you see a shark, report it to Water Police immediately on 9442 8600.
Public report unknown sp. shark sighted 17:00hrs 28/04, Gearys, south of Mandurah 50m offshore , surfer bumped hard by poss shark .— Surf Life Saving WA (@SLSWA) April 28, 2018
Fisheries advise shark warning at Gearys Beach South of Mandurah after surfer knocked off board by unknown species of shark for more information see:— Surf Life Saving WA (@SLSWA) April 28, 2018