Ships have been put on alert after an iceberg was spotted floating off St Francis Bay in the Eastern Cape, the Cape Argus reported on Tuesday.
The large white mass, said to be about 35 nautical miles offshore, is estimated to be 25m long and 20m high.
It was reported by a single vessel, the Ntini, which was sailing in the area on Monday night.
The National Sea Rescue Institute issued an immediate maritime radio warning to vessels to prevent a possible collision, the newspaper reported.
NSRI spokesperson Craig Lambinon said the NSRI did not know which direction the ice mass was drifting, how fast it was travelling and at what rate it was melting.
By 9am on Tuesday, no other vessels had reported sightings, the Argus said.
Lambinon said an iceberg had been reported off Port Elizabeth in the 1950s.
St Francis Bay is about 100km from Port Elizabeth.
Dr John Rogers, a senior researcher in the Department of Geological Sciences at the University of Cape Town, told the Cape Argus that an iceberg was usually about eight times bigger underwater than it was above the surface.
”So if the iceberg is 20m high above the surface, it means there’s another 160m of iceberg below the waterline,” he said.
He said that if the iceberg did in fact exist, it was possible it had been pushed towards the shore by a major eddy from a current flowing eastwards towards Australia.
It was possible for an iceberg to ground itself on the outer shelf of the Agulhas bank before it reached the shore, Rogers said.
He said scientific papers said that the British Navy reported an iceberg about 60 nautical miles off Cape Point in the 1800s.
Rogers said it was common knowledge that bigger chunks of ice in the Antarctic were breaking off because of global warming. — Sapa