"Due to the lack of sand, rocks hitting the poles and the force of the waves, the poles have come out and they're gone."
The ramp used to move inflatable rescue boats from St Clair Surf Life Saving Club to the beach was "completely destroyed".
The club's main concern was "in-water safety" of swimmers and the absence of inflatable boats, which would make it unsafe for the plunge to proceed, he said.
The club wanted people to stay away from the beach for about three weeks.
It was hoped the plunge would be held in mid- to late July, if conditions improved, he said.
The possibility of the plunge moving to Middle Beach was discussed but the access was unsafe because the sand dunes had been washed away.
"In the past, we have been able to move it down the beach, but this is the first time I can recall it being postponed to a later date, or possibly not be held at all."
Dunedin City Council roading maintenance engineer Peter Standring said "mean seas" washed poles from the piers on St Clair Beach.
The three piers were installed in the 1900s and were designed to trap sand.
"They have stood the test of time, but it's pretty challenging at the moment .. . this might be their time."
The poles were council property. The council had no plans to "resurrect" the poles, if recovered, in the piers.
