Bulli Beach closed for more than an hour on Wednesday after two sharks were spotted off Sandon Point.
Swimmers at neighbouring beaches were also warned to stay close to the shore.
A lifeguard patrolling the water on a jetski spotted the sharks at 2.45pm about 200 metres from Bulli Beach, said Illawarra Surf Life Saving duty officer Lachlan Pritchard.
He said the sharks were three to four metres long.
Bulli Beach was closed while lifeguards waited for an aerial sweep of the beach.
Bendigo Bank Aerial Patrol general manager Harry Mitchell said the aircraft was asked to head to Bulli Beach around 4.15pm to confirm the status of the area after the earlier shark sighting.
‘‘The aerial patrol advised Surf Comms that it had not sighted a shark. However a large stingray was spotted in the swim zone close to swimmers,’’ Mr Mitchell said.
‘‘Another request to confirm a shark sighting at Port Kembla Beach resulted in the sighting of a shark about 400 metres from shore.’’
Mr Mitchell said up to seven sharks were sighted on Wednesday afternoon in a routine aerial patrol of Illawarra and South Coast beaches.
At about 2.30pm, two large hammerhead sharks and a third unidentified species were seen near the entrance to Lake Conjola.
‘‘The sharks were 50 metres from shore and did not pose a threat as there were no swimmers nearby,’’ Mr Mitchell said.
Shortly after 3pm, five large sharks were seen at Vincentia and Hyams Beach in Jervis Bay; the largest was estimated at four to five metres long and possibly a tiger shark.
The aerial patrol sounded the siren to evacuate up to 70 people from the water and spent almost 40 minutes over the beach maintaining a watch of the sharks’ movements while police were called to manage the situation on the ground.
“Jervis Bay beaches are not patrolled by beach safety providers and swimmers rely on the aerial patrol to provide warnings of potential threats to safety,’’ Mr Mitchell said.
He argued the shark sightings contradicted a report earlier this week by the Department of Primary Industries that aerial surveillance of shark movements was ineffective.
He said his crews are on heightened alert for increased activity as the water warms up and fish shoals become more abundant along the coast.