On Friday morning, May 21, beaches from Black Head to One Mile were reopened.

Beaches further north and closer to the scene of the attack remained closed.

A 59-year-old man from Sydney's northern beaches, later identified as Mark Sanguinetti, was pulled from the water on Tuesday and officers from Manning Great Lakes Police District commenced CPR. He died at the scene.

Department of Primary Industries advised tagged white sharks were detected by receivers at Bennetts Beach (Hawks Nest), Forster Main Beach in the early hours of Friday morning.

A 2.88m great white was tagged and released from the drumline at Forster Main Beach on Thursday morning.

On Wednesday, several great whites up to 2.5m in length were tagged and released from Tuncurry Beach and Main Beach. A 3.2m great white was also sighted further north at Crowdy Head.

Last Sunday, Old Bar Beach was closed due to 'shark activity'.

Meanwhile, Triathlon NSW has created an alternative plan for concerned participants in tomorrow's Club Championships in Forster.

If beaches are declared safe and open in time for the championships, participants will be able to compete in the original format (swim, bike, run) or complete a duathlon (run, bike, run). If the beaches remain closed, the race will become a duathlon.

Organisers will implement spotters on the beach, a drone, additional rescue boards and IRBs if the swim proceeds.