Blacksmiths beach was closed for about an hour on Monday after a "large" shark was spotted close to shore.
Lake Macquarie City Council lifeguards cleared the beach about 1.30pm after receiving reports of what appeared to be a shark in the water.
Lifeguards launched a jetski and spotted a "three to four metre" shark before it headed offshore, council's lifeguard services manager Paul Stone said.
"Reports are there was a bit of size to it," Mr Stone said.
"The lifeguards did see it and confirm it. They said between three and four metres. It just took off out to sea and that was the end of it.
"We left the beach closed for about an hour beyond that."
Mr Stone said the species was not known, but given the size "our default thought process is probably a great white".
Mr Stone said it was the first shark sighting at one of Lake Macquarie's four council-patrolled beaches since "early in the season".
"We had a few sightings very early in the season through September and October but since then it has been fairly quiet," he said.
"We had an activation at the Redhead shark buoy at the weekend ... but there's no indication what activated up there was linked to what happened today.
"But in general we haven't had a lot of sightings this season compared to seasons in the past."
