UPDATE: 12.45pm Fisheries has spotted 3m shark 1.3km off Meelup Beach.
Surf Life Saving WA said the shark was spotted at 12.15pm and was heading north.
It was not known what type of shark it was.
A 5m shark was spotted 500m off Geordie Bay at Rottnest. Surf Life Saving WA tweeted the sighting at 10.20am.
The Westpac Rescue Helicopter sighted two 3m sharks 100m offshore at north Floreat this morning but the beach has been reopened.
Surf Life Saving WA tweeted the sighting at 9.10am.