Hyams Beach was closed on Wednesday and Thursday after 50 sharks were detected in the area, 20 of them close to shore while swimmers and divers were in the water. 

On Thursday, a school of 12 sharks were spotted "two or three paces" into the water at the tourist spot, prompting the council to evacuate swimmers, call the Westpac Rescue Helicopter to patrol, and organise lifesavers to patrol for the next two weeks.

On Friday morning, at least one possible shark sighting was reported as more than 400 people flocked to the beach.

A woman preparing to swim with her children spotted a dark shape in the water and "panicked" before returning to her nearby holiday accommodation.

The woman alerted her husband, and reports made their way to a local marine rescue organisation.

Pictures taken from the air on Thursday afternoon showed the sharks close to the shore, where swimmers stood with their towels at the ready.

Harry Mitchell, who has run the shark-watching Bendigo Bank Aerial Patrol for the past 25 years, said he has seen more than 100 sharks close to the shore from Stanwell Park to Jervis Bay in the past three days.

"It's not unusual to see sharks close to shore at popular beaches at this time of year, however over the past three days we've seen in the vicinity of 100 sharks across three local government areas in the Illawarra and Shoalhaven," Mr Mitchell said.

The sharks at Jervis Bay appeared to be whalers, while Wollongong and Shellharbour saw "predominantly hammerheads".

A siren was sounded by the aerial patrol's plane when the whalers came within metres of swimmers at Hyams Beach.

"We've seen sharks three to four metres away from people," Mr Mitchell said. "Whilst they didn't look threatening, and I stress that, the sharks didn't look threatening, we have a duty of care and we have to alert the beach-going community that there is a potential threat.

"Some of those sharks yesterday and the day before were quite large, between two and a half and three and a half metres in length. Some of them were in water only a metre deep."

It's believed the sharks were brought close to shore by food sources and relatively warm water.

Duncan Leadbitter, a visiting fellow at the Australian National Centre for Ocean Resources and Security who is also a volunteer with the aerial patrol, said such numbers of sharks are "uncommon".

"Our records had 50 sharks in Jervis Bay alone," Mr Leadbitter said.

"It seems to be a place where we see a lot of young ones [whalers] at this time of year," he said, after checking records dating back 15 years.

Despite this, he said the South Coast has "absolutely" missed out on funding for beach safety initiatives under the Baird Government's multimillion dollar shark strategy, which has instead focused on the north coast and metropolitan Sydney.

"From Wollongong south there is six times the number of sharks that you would see in the Sydney region, and the number of fatalities in our patrol area is no different. People would like to see a lot more advisory work here," he said.

Mr Leadbitter said the patrol believes there are more sharks off southern beaches than they are able to see, and they want $100,000 to deploy "hyper spectral scanner" technology that has been developed in Western Australia.

Steve Jones, the South Coast president of Surf Life Saving NSW, said sharks had always been seen off the beach and around the rocks in the area, but the difference this time is the sharks were in greater numbers than normal.

He said swimmers flocked to the small patch of sand in their hundreds while he was at Hyams Beach on Friday morning, seemingly undeterred by the previous beach closures.

"We had two groups of people pull up to us and say 'do you think there's going to be any sharks here today'," Mr Jones said.

They were told the sharks were always there, just further out into the water, and swimmers would be warned if they came close to shore.

"They said 'OK' and went down to the beach," he said.

A boat from Jervis Bay Marine Park was out on Friday morning inspecting the water. The Department of Primary Industries directed inquiries to Surf Life Saving NSW.

Richard Walker, the floor manager of the Hyams Beach Store and Cafe, said patrons had mentioned shark sightings over the past few days.

"It's not an uncommon thing to see sharks off the beach, they just seem to come to prominence when the tourists come here and they bring the shark planes out," he said.

A massive boom in the number of people visiting beaches is the main reason sharks are occupying such a prominent position in our summer this year, surf life savers say.

Figures show an explosion in beach visitation in the Illawarra of more than 200 per cent since 2009, and more people on the beach means more chance of an encounter with marine predators in their natural environment.

Add this to several well-publicised shark attacks on humans on the NSW coast in 2015, and the dozens of sharks spotted between Port Kembla and Jervis Bay this week – including the pack of bronze whalers in the swimming zone at Hyams Beach.

Friends of the shark may not want to admit it but the reality is many people will reasonably be a bit more wary of them this summer. And this is not a bad thing, Surf Life Saving South Coast president Steve Jones said.

“It’s an individual personal assessment,” he said.

“It’s not about creating anxiety. It’s about keeping people calm. 

“People who have seen reports [of shark attacks] become alert, and in some cases become alarmed. They see a shadow in the water it alerts them. Sensibly it’s a good thing because if you think it’s a shark you should get out of the water until it goes away.”

He has circulated a checklist of advice for beachgoers on how to minimise the risk from sharks, and what to do if you encounter one.

It was not one but more than a dozen large sharks making beachgoers uneasy at Hyams Beach in Jervis Bay on Wednesday and Thursday.

When the Mercury flew over Jervis Bay with the Bendigo Bank Aerial Patrol on Thursday several large sharks were easily spotted near beaches.

Mr Jones said up to 20 sharks were coming in near swimmers, with about 500 people on the beach. Some people refused to get out of the water until the sharks were “a few metres” away.

Airborne spotters identified the sharks as bronze whalers up to 3.5m long – a species which is known to come close to shore to feed, and while not identified as the most dangerous, can be aggressive towards people.

Mr Jones said there were always sharks in the bay but the massive increase in visitors in recent years made encounters more likely.

It’s not just Jervis Bay. Figures calculated by Surf Life Saving NSW and provided to the NSW Government show attendance at Illawarra beaches has increased by more than 200 per cent over five years - from 124,000 in 2009-10 to more than 392,000 in 2014-15.

The visitation figures are worked out by counting the number of people on five Illawarra beaches at 1pm from September 25 to April 25. The beaches are Coledale, Austinmer, Thirroul, North Wollongong and Wollongong City (south beach).

The figures are not exhaustive but have been calculated the same way over the six years, allowing genuine comparisons. Similar increases have been reported in Sydney and the Central Coast, and in the Hunter the increase has been more than 460 per cent.

After Wednesday Shoalhaven City Council agreed to his request for lifesavers to be stationed at Hyams Beach for two weeks.

The Aerial Patrol’s Harry Mitchell said there had been dozens of sharks spotted this week, with five hammerheads closing Warilla beach on Wednesday.

- Ben Langford