The NSRI were contacted around 4pm to assist, spokesman Craig Lambinon said.
Municipal protection services, police, private, and provincial emergency services also responded.
“On arrival on-scene a search commenced for a 22-year-old Zimbabwean man reported to have disappeared under water after being swept out to sea by rip currents while swimming,” said Lambinon.
“Eye witnesses on the shore and protection services members, who had arrived on scene first, identified the place, on the water, where the man had last been seen.”
An extensive sea and shore search was conducted, following the sea currents, but no sign of the missing man was found.
Police and emergency services assisted the man’s brother who had been at the beach with him at the time.
“Police are investigating and a police dive unit has been activated to continue a search from tomorrow [Wednesday] morning,” said Lambinon.