Shark keeps Newcastle beaches closed

Newcastle beach inspectors say it's too risky to reopen beaches with a five-metre shark lurking near the coast for a fifth straight day.

A great white shark of this size could bite someone in half, says Nobbys Beach inspector Paul Bernard.

"You don't get a second chance with these things, [a] bite can be fatal," he told AAP.

"We've never had a shark this size hanging around."

The inspector, who was just metres away from the shark during a jet ski beach patrol, said it had been sighted numerous times.

The shark was last seen by water police in a boat at about 2.30pm on Tuesday at Burwood Beach, near Merewether Beach where it was first sighted on Saturday afternoon.

As a result, beaches have remained closed for a record fifth day in a row.

Mr Bernard said the council was taking the decision seriously, especially as beach kiosks and businesses could be affected.

"Would I go into the water? Would I put my kids in the water? No," Mr Bernard said.

"I didn't even go ocean ski paddling on my day off yesterday."

The shark has been sighted in an area stretching 10km to 12km.

Increased marine activity and overcast and warm weather are thought to be possible reasons for the shark's prolonged presence.

Rob Townsend, life sciences manager at Manly Sea Life Sanctuary, has said the shark's behaviour was not unusual.

"Great whites are very variable," he said.

"They spend time in the surf where they are sometimes spotted by lifeguards and then they also have their massive oceanic migration where they travel to South Africa.

"They are very adaptable."

The latest helicopter search, which was conducted late on Tuesday afternoon, found no sign of the shark.