An eight-year-old girl and a teenager were feared missing out at sea off different parts of the country on Wednesday, SABC radio news reports.
The search for the girl, off Mouille Point on the Cape Peninsula, involved two boats and a helicopter on Tuesday.
The National Sea Rescue Institute has since handed over the search to the police.
Meanwhile, on the other side of the country, off Port St John's in the Eastern Cape, a 15-year-old boy is missing after possibly having been attacked by a shark.
He had been bathing with several other people at Second Beach, where there has been a string of fatal shark attacks in recent years.