A Victorian man said he was supposed to meet his twin brother at an isolated beach near Tathra in NSW last week but all he had found was a pile of clothes and other belongings.

A camper said the 42-year-old asked people on the beach if they'd seen his twin about 2.15pm. Other witnesses say the missing man had gone for a run and a swim in the ocean.

Emergency services were called about 5.30pm as darkness fell on Gillards Beach in the Mimosa Rocks National Park.

Emergency services launched a three-day desperate search for a missing man. Credit:Marine Rescue NSW

A desperate air and sea search for the missing brother began, with teams from surf lifesaving clubs, Merimbula and Bermagui Marine Rescue, Bega Valley SES volunteers, NSW Ambulance, PolAir and the Westpac Rescue Helicopter.