Two full days of searching have failed to find any trace of a whitebaiter missing after he was swept out to sea at the Rakaia River mouth.

Victor Boraman, a 21-year-old dairy worker who was originally from Oamaru but moved to Ashburton a few months ago to work on a dairy farm, has not been seen since he was swept away while whitebaiting with two friends at the mouth on Sunday night.

Searchers have ventured as far north as Lake Ellesmere over the past two days, but generally the search area is focused around the area 2-4km either side of the Rakaia River mouth.

A fixed wing aircraft from the Coastguard Canterbury Air Patrol was tonight due to join the search for the second evening running, while Land Search and Rescue (LandSAR) volunteers scoured the shoreline.

Search co-ordinator Sergeant Ryan O'Rourke said further shoreline searches were undertaken yesterday afternoon, using LandSAR volunteers from the Rakaia and Ellesmere groups.

About 10 LandSAR volunteers were involved on both south sides of the river, but neither group found any trace of Mr Boraman.

They then used quadbikes to search along the beach at low tide, about 5.30pm.

Mr O'Rourke said conditions in the area today were again poor, with low cloud and poor visibility.

Mr Boraman was swept into the sea about 7pm on Sunday while whitebaiting with friends. According to his mum Dixie Boraman her son's dog had taken off and got into the lagoon. His friends grabbed the dog and when they turned around a wave had come in from behind Mr Boraman and knocked him off his feet.

Police said Mr Boraman did everything right. It's understood he took his waders off so that he could float as attempts were made to rescue him.

Mr O'Rourke said conditions at the time were rough, with strong winds and large waves.

No trace of Mr Boraman has been found since he was seen in the water by a Westpac Rescue Helicopter crew about 8pm on Sunday. The helicopter was unable to complete a rescue due to the difficult conditions, but came agonisingly close.

Survival chances after so long in such cold and unpredictable waters were not good, but Mr Boraman's family had their fingers crossed the sea would return their son to them.

Mr Boraman came to New Zealand as a six-year-old when his parents brought him out from Russia, where he'd been an orphan.

Shoreline searches for him will continue through until Friday if required.

- APNZ