Lifeguarding Australia's Stan Wall said four unidentified sharks were spotted between Broulee Beach and South Head beach on Monday morning.

The sharks, one of which was 2.5 metres long, kept returning to the area forcing authorities to close the beaches.

"We don't want people going into the water there," he said.

The sharks were first spotted by a Department of Primary Industries aerial patrol, while the Westpac rescue helicopter and lifeguards later confirmed the sightings.

Authorities also cleared swimmers from the water at Kiama's Surf Beach and Kendalls Beach after a 2.5-metre bull shark was spotted about 100 metres off shore on Monday.

Surf lifesaving volunteers spotted the creature while manning a drone over the coastline about 1.45pm.

Kiama's casual lifeguard supervisor, Craig Bowley, said the shark's close proximity and its species - bull sharks are known to be aggressive - prompted the hasty warning.

"The beach is closed until further notice," he said about 2.25pm.

Drone operators have been positioned near the beach's southern end throughout the summer holidays as part of a new shark-spotting program, which replaces a shark-spotting blimp that was seen over area beaches last summer.

Kiama club captain John Ford said the surveillance would continue every day throughout the school holidays.

It is understood this was the first sighting to come from the Kiama drone so far this season.

Surf Life Saving NSW began a drone surveillance program at nine of the state’s beaches in 2017. This year it spread to Kiama, Mollymook, Pambula and Tathra. Surf Life Saving NSW is in the process of rolling out the program to more beaches..

A two-metre white shark was also spotted at Bherwerre near Sussex Inlet, also on the south coast, about noon on Monday.

with Illawarra Mercury