Premier Mike Baird's announcement yesterday that the state government will spend $100,000 trialling a sonar-based shark detection system at NSW beaches is just the latest in a very long line of ways that Australians have tried to protect themselves from the ocean's most fearsome predator.

It follows a string of shark run-ins in NSW – beaches were closed for 10 days in Newcastle this month as a large great white shark came too close to the coast for comfort, and both Bondi and Manly beaches have been closed due to shark sightings in the last few months.

But the declaration of a new approach to shark control following a flurry of shark encounters is not a new cycle. Beachgoers might wonder what happened to the drone trials announced in 2013 by the state government after the death of 19-year-old bodyboarder Zac Young near Coffs Harbour.

Surf Life Saving Australia also experimented with using drones to spot sharks and rescue swimmers in Queensland, but the technical restrictions and cost saw its trials scaled back, according to the organisation's coastal risk and safety manager Anthony Bradstreet.

"We did trial a few platforms ... but since then we've had bit more of a feasibility analysis," Mr Bradstreet said.

He said that smaller, cheaper drones required the operator to keep a line of sight with the aircraft. They are also limited to between 45 minutes and an hour in the air.

"If the micro-drones are off the table then you start looking at [drones] that have a longer endurance," Mr Bradstreet said.

"They're generally the ones that are coming out of defence ... [and] obviously come at a higher cost and a much higher regulatory burden."

"The mark one eyeball is always promoted as being the best surveillance instrument around."

Swimmers can also take matters into their own hands, with an apparently shark-resistant wetsuit that uses colours and camouflage to confuse sharks.

And last year, the government of Western Australia provoked national outrage over its plans to cull sharks using baited hooks. Rob Townsend, the life sciences manager at Manly Sea Life Sanctuary, argues that the shark nets used on 51 NSW beaches between Newcastle and the Illawarra are no different.

"The popular conception is that [shark nets are] a big fence that sort of stops sharks going to beaches," Mr Townsend said.

"They're actually designed to kill sharks, the idea being that if a shark is showing a propensity to hang around beaches then that's a particular individual we want to remove from the population."

Greens environment spokesperson Dr Mehreen Faruqi used the announcement of the sonar system yesterday to push for the removal of the state's shark nets.

"Shark netting has killed thousands of threatened species including dugongs, rays, turtles and the critically endangered grey nurse sharks, and it only gives an illusion of safety for beachgoers," she said.

Nets have been used in NSW since 1935, but Mr Townsend said that most swimmers would probably never need the myriad systems such as drones and sonar buoys developed for extra protection.

"Very rarely, if ever, have I heard of someone who was swimming between the flags at a busy beach being hassled by a shark," he said.