UPDATE 3:20pm The search for a swimmer off Trigg Beach has been suspended after no firm reports of a missing person were received.
Police and surf lifesavers had been searching the water and the beach from more than three hours after a beach inspector saw a man waving for assistance about 11:30am but couldn't locate him a short time later.
Rescue boats, helicopters and jetskis were all used in the search while beachgoers were ordered off the beach and asked to take their towels so police could search for the man's belongings.
The situation was further complicated after a 1.5m hammerhead shark was spotted 300m off the beach about 1:50pm.
At this stage it is believed the man may have managed to make his way back to the beach unaided.
The helicopters swept a large area of water stretching down to South Trigg in an effort to locate the man.
A Surfing WA event was postponed due to the search.
Police are asking anyone who knows of loved ones swimming at Trigg and are concerned they have not returned home to call 131 444.
Earlier, a 61-year-old woman at Swanbourne Beach and a man at City Beach were both treated for spinal injuries as a larger swell caught out swimmers across Perth.