A large-scale search for two European tourists who went missing at a beach near Port Macquarie has resumed on NSW's mid-north coast.

Hugo Palmer and Erwan Ferrieux, both aged 20, haven't been seen since passers-by found their personal items at Shelley Beach on Monday morning.

Their rental car was found in a nearby carpark with a number of other belongings - including travel documents - still inside.

One local claims to have seen towels and gear belonging to Mr Palmer and Mr Ferrieux on the sand late Sunday afternoon, raising questions about when the pair arrived at the beach.

"There was no sight of them anywhere then," the man wrote on Facebook on Tuesday as authorities scoured the coast.

A ground and water search involving police divers, Marine Rescue, the State Emergency Service and others resumed this morning.

Mr Palmer, an Englishman, and Mr Ferrieux, a Frenchman, have been close friends for years, according to their Facebook pages.

They both appear to have attended Sackville School, south of London.

Police have been communicating with both the British and French consulates about the missing men.