Malua Bay Beach in New South Wales shut promptly on Monday after several sharks swam close to the shore.
Officials told everyone to get out of the water without delay when big sharks appeared in shallow waves.
A 3.45-metre tiger shark, predator, just fitted with a identification device, was spotted nearby.
Local encounters have been increasing.
The beach stayed shut while coast guard checked the zone.
No one near the sharks got was unharmed.