Emergency services were called to the Batemans Bay Marina, on the NSW south coast, on Saturday night after a 56-year-old man was reported missing.
The man left the marina about 6am in an eight-metre Arvor cruiser for a day's fishing trip.
He was spoken to about 10am but has not been heard from since.
When he failed to return to the marina on Saturday evening, emergency services were called in to try and find him.
Marine Area Command and Marine Rescue NSW crews, a fixed-wing aircraft and a helicopter searched offshore waters until nearly 1am, but neither the man nor his boat was found.
"The Marine Rescue Batemans Bay and Bermagui crews said sea conditions were favourable last night, but it was quite dark with little assistance from the moon, and they had to navigate around numerous whales," Marine Rescue NSW Inspector Stuart Massey said.
The search restarted on Sunday with dozens of volunteers, six boats, aircraft and Surf Life Saving NSW deployed to help find the man.
Insp Massey said sea conditions are favourable again on Sunday morning with good visibility for the volunteers scouring the ocean for the missing man.
"They are searching an area offshore from just north of Narooma to south of Bermagui under the direction of Marine Area Command and will continue to do so until otherwise instructed," he said.
9°C