The warning follows the death of 19-year-old Zac Young at Coffs Harbour on Saturday after he was mauled by a shark while surfing.

The week before, a 35-year-old man was attacked by a shark and killed while surfing 270 kilometres south of Perth.

Aerial patrol general manager Harry Mitchell said large schools of fish which attract sharks had already been seen off the coast.

"That is going to bring marine life closer to our coastline and closer to our beaches," he said.

The Illawarra's last recorded shark attack was in 2009 when Steven Fogarty was bitten while snorkelling in Lake Illawarra.

He was treated in hospital for more than 40 puncture wounds to his right calf.

Last year, the Bendigo Bank Aerial Patrol began trialling a new patrol schedule, operating daily from mid December and ending in late January to coincide with the school holidays. Traditionally, the service has operated only at weekends and public holidays.

Mr Mitchell said the decision had been made to make better use of funding, and so far had been a success.

"That six-week period is when beaches are most populated and tourism levels are up with people from all over the state, interstate, and even overseas," he said.

This year, the patrol will begin its daily flights on December 20.

Mr Mitchell said sharks were most often spotted near the entrance to Lake Illawarra and other estuaries, as well as the notorious "shark alley", between Austinmer and Coalcliff.

In the event a shark is sighted, an aerial patrol crew member will contact lifesavers at the nearest beach, who will inform swimmers.

While there was a need for caution, there was no need to avoid the beach altogether, Mr Mitchell said.

"You've got a better chance of winning Lotto than getting taken by a shark," he said.

The Bendigo Bank Aerial Patrol is funded entirely by the community, including Wollongong, Kiama, Shellharbour and Shoalhaven councils, and sponsorship partners.