The St Clair Beach Polar Plunge has been postponed as the area has become unsafe to access.
The annual event, which has people rushing into the cold ocean, was due to be held on Sunday for its 94th year.
Many swimmers dress up in costume to brave the waves.
St Clair Surf Life Saving Club chairman Cam Burrow said the beach had been "taking a hammering" with the recent weather and a lot of sand had been eroded away.
There was no safe way to access the beach, including through the alternative path by the St Clair Scout Hall and tennis courts.