Swimmers have been called to leave the water after a school of sharks have been spotted cruising close to the shore at the popular Sydney beach on Tuesday morning.

It is understood that up to 15 hammerheads got within metres of swimmers at Palm Beach, prompting an alarm to be raised around 1pm.

The beach was shut and flags taken down as lifeguards monitored the situation from the water on jet skis and from the sand.

Swimmers have since been able to return to the water at Palm Beach. The sighting comes a week after another hammerhead shark was spotted at the same iconic beach.

Australia has not recorded a human fatality from an attack by a hammerhead shark, according the Australian Marine Conservation Society website.

The event has renewed debate on the use of shark nets in NSW, with some saying sightings should not cause alarm.

There are 15 shark nets on the Northern Beaches between Palm Beach and Manly.

“With all the new drones that the beach patrols have these days they can monitor the sharks, shark nets only tangle up other sea life,” one person said on social media.

“Sharks being sharks in their own environment, who would have thought?” another said.

Image: Getty

This article first appeared on Over60.