NSW South Coast District Inspector Peter Volf said the police search will continue on Friday at sea via the NSW Police Marine Area Command after Thursday's land search found no trace of the missing man.

Cheryl McCarthy, director of lifesaving for the Far South Coast branch said three rescue boats and a jetski were to conduct a looped search of the area on Friday morning.

"The sea conditions are a lot lower, so we can get closer to the rocks. We've been able to check them with our drone and a helicopter," she said.

Ms McCarthy said the search will likely be terminated for the day around midday.

The man was reported missing around 5.30pm on Wednesday after witnesses reported seeing him go for a run and a swim at the popular yet remote tourist beach inside Mimosa Rocks National Park.

He had been traveling through the region with his twin brother, who after arriving at the beach around lunchtime on Wednesday travelled back to Tathra before returning to the beach around 2.30pm, finding only his brother's clothes and personal belongings left on the beach.

South Coast Police District police officers soon commenced a search of the area for the man, coordinated by the Marine Area Command and with help from the State Emergency Service, NSW Ambulance, Surf Rescue NSW and PolAir.

At least 30 personnel took part in the search on Thursday, and the Westpac Life Saver Rescue Helicopter continued the search for the man on Friday.

Police said if the search fails to locate the man a missing persons inquiry will continue.

AS IT HAPPENED: Live coverage of Thursday's search efforts