SURF Lifesavers have sighted a 3.1-metre unknown species of shark near the Dawesville Channel.
The shark was sighted at 9.40am, 70m offshore and 200m north of The Cut in close proximity to surfers.
The surfers have been cleared from the water by the helo.
Pyramids Beach was re-opened early this morning after Wednesday's shark attack which saw a 18-year-old bitten on the foot by a Grey Nurse shark.
The City of Mandurah along with the Surf Life Saving Association and Department of Fisheries have closed Pyramids Beach with visibility poor.
A watch and act warning has been issued.
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