Time is running out to save a father and son who are missing off the NSW south coast after failing to return from a rock-fishing trip.

A multi-pronged search effort involving police divers, SES officials and rescue specialists are on the scene after the pair did not return to their home in southwest Sydney.

The father, aged 47, and his son, 17, who live in Liverpool in southwest Sydney, set off on Monday to fish at Storm Bay near the popular Kiama Blowhole, about 115km south of Sydney.

Police were called over concerns for the duo’s welfare at 3am on Tuesday and Marine Rescue said it deployed a search boat from nearby Port Kembla at 7.30am.

Given the pair’s fishing gear had been found and there had been no communication from them, NSW Police Superintendent Craig Ireland said the working assumption was they had gone into the water.

“There’s a lot of people actively trying to find these two fellas … (there’s) still hope, (we) never give up, but as time ticks on that hope diminishes,” he said.

The wife and mother of the missing fishermen was distraught, Supt Ireland said.

“The best-case scenario is they’ve found something, a flotation-type material they can hang onto,” he said.

“They are capable swimmers, we know that, but there’s been no sightings of them, so we’re just hoping for the best.”

Police will continue the search but said post-sunset conditions would be too dangerous to continue.

Marine Rescue NSW is also searching, as are police helicopters and Surf Life Saving NSW officials.

“The Marine Rescue NSW crew … will assist Port Kembla Water Police with a coastal contour search in waters off Kiama Blowhole after the two people reportedly failed to return from a fishing trip early last night,” Marine Rescue NSW inspector Stuart Massey said.

“The crew has just joined the search under the direction of NSW Police Marine Area Command … sea conditions off Kiama are fair.”